Scientific Program

Conference Series Ltd invites all the participants across the globe to attend 4th International Conference on Physical and Theoretical Chemistry Dublin, Ireland.

Day 1 :

Physical Chemistry 2017 International Conference Keynote Speaker Stefan Haacke photo
Biography:

Stefan Haacke is professor in Physics at Strasbourg University and Director of the Institute of Physics and Chemistry of Materials Strasbourg. His research on ultrafast spectroscopy of biologic molecules and organic nanostructures has been published in 114 papers, and a multi-author book co-edited w. Irene Burghardt (Frankfurt). Present international collaborations involve partners at the National Seoul University, Sogang University Seoul, Nagoya Institute of Technology, Bowling Green University Ohio, University of Siena and the University of Frankfurt. He is coordinator of the French-German project Femto-ASR, on the ultrafast photochemistry of Anabaena Sensory Rhodpsin and its mutants, and partner in the projects FemtoDNA, 2D femtosecond UV spectroscopy applied to labeled DNA double strands, and PhotIron. Most notable is his membership in the advisory board of the Int. Conf. on Photochemistry (ICP) that will be held in Strasbourg in July 2017.

Abstract:

Over last decades, transition metal complexes (Pt, Ir and Ru) have received great attention due to their long-lived electronic excited states, for applications such as OLEDs and dye-sensitized solar cells (DSSCs). However, the replacement of these expensive, scarce and toxic metals by earth-abundant metals such as Fe or Cu is still extremely challenging due to very short excited state lifetimes of the metal-to-ligand charge transfer states (MLCT), limited, in the case of Fe, by spin cross-over into metal-centered high spin states as observed in Fe-pyridine complexes[1].

A possible way to stabilize the lowest energy triplet 3MLCT energetically and thus temporally is to increase the ligand field strength by chemical design. Recently, the use of N-heterocyclic carbenes (NHC) ligands was reported to lead to a prolonged 3MLCT lifetime (9 ps)[2], which we were able to extend up to 16.5 ps due to carboxylation of the ligands[3] (fig. A). Very recently, the Wärnmark group working on the same carboxylated complex, reported efficient electron injection into TiO2 by using THz spectroscopy, but also deleterious charge recombination.[4]

We have designed new complexes where iron was coordinated by benzimidazolylidene-based (Biz) which affords a new record 3MLCT lifetime of 26 ps in MeCN.[5] Streak camera fluorescence experiments on complexes grafted on TiO2 and Al2O3 substrates indicate electron injection through shorter 3MLCT state lifetime on TiO2 than on high-band gap Al2O3 (fig. B), but also surprisingly long 3MLCT state lifetime components induced only through binding on the semiconductor surfaces. A detailed modeling of the effect of surface attachment on the excited state ordering is in progress.

Research is funded by the ANR projet PhotIron.

(A) Kinetic traces of excited state absorption (ΔA>0, red) and ground state bleach (ΔA<0, blue) GSB of Iron complexes. 3MLCT lifetimes are 16.5 ps (Fe(CarbenCOOH)2) and 26ps (Fe(BizCOOH)2) in MeCN. (B) Kinetic traces of 3MLCT of Iron complexes grafted on TiO2 and Al2O3.

Physical Chemistry 2017 International Conference Keynote Speaker Junrong Zheng photo
Biography:

Prof. Junrong Zheng completed his PhD and postdoctoral studies from Stanford University. He is professor of chemistry at Peking University, and a co-founder of Uptek Solutions, a Long-Island-based laser company. He is a recipient of numerous prestigious awards including the Sloan Fellowship and the Packard Fellowship.

Abstract:

Electron/hole transformations on interfaces determine fundamental properties of opto-electro-chemical devices, but remain a grand challenge to experimentally investigate and theoretically describe. Herein combining ultrafast VIS/NIR/MIR frequency-mixed microspectroscopy and state-of-the-art two-dimensional atomic device fabrications, we are able to directly monitor the phase transitions of charged quasiparticles in real time on the ultimate interfaces – between two atomic layers. On type II semiconductor/semiconductor interfaces between two transition metal dichalcogenide (TMDC) monolayers, interfacial charge transfers occur within 50fs and interlayer hot excitons (unbound interlayer e/h pairs) are the necessary intermediate of the process for both energy and momentum conservations. On semiconductor/conductor (graphene) interfaces, interlayer charge transfers result in an unexpected transformation of conducting free carriers into insulating interlayer excitons between the conducting graphene and the semiconducting TMDC. The formation of interlayer excitons significantly improves the charge separation efficiency between the two atomic layers for more than twenty times.

FIG. 1. Interlayer charge transfers between MoSe2/WS2 atomic layers.  The interlayer charge transfers (<50fs) result in the formation of interlayer hot excitons, much faster than the formation of intralayer excitons (~600fs).

Physical Chemistry 2017 International Conference Keynote Speaker Elena G. Kovaleva photo
Biography:

Elena G. Kovaleva has her expertise in electrosurface and electrocapillary  phenomena in inorganic nanoporous and nanosized systems, organo-inorganic hybride materials, ion-exchange resins by EPR of pH-sensitive nitroxides as spin probes and labels as well as other paramagnetic particles as Сu2+, Co3+, Mn2+, Cr3+. Recently she developed the technique for determination of local acidity and near-surface (Stern) potential in porous and nanostructured  hydrated materials. She is currently working on the problem of the effect of electrostatic properties of a charged surface on catalytic activity heterogeneous catalysts carrying industrial enzymes.

Abstract:

Statement of the Problem: Many solid-phase materials , for instance, porous and nanostructural objects as well as the systems of specific functionality are widely used in aqueous solutions as promising heterogeneous catalysts of various reactions, can serve as suitable carriers for catalytically active organic and bioorganic groups and enzymes, and also be adsorbents of large and small molecules. The properties of solid-phase materials are affected therefore both the chemical nature of the solution and some specific conditions arising in the phase and on the surface of these materials.  Surface electrical potential (SEP) is among the most important surface characteristics of these materials. At present, there is no method for measuring SEP of hydrated porous and nanostructured materials. The purpose of this study is to develop the method for measuring SEP of different solid phase hydrated materials by EPR of pH sensitive nitroxides (NR) as spin probes and labels. Methodology & Theoretical Orientation: A variety of nitroxides with the range of pH-sensitivity from 2 to 8.5 pH were incorporated into nanoporous and nanostructured inorganic oxides as powders and membranes and a diversity of organo-inorganic hybride materials both by adsorption from aqueous solution and through covalent binding technique. pH-dependent parameters of EPR spectra were measured through monitoring pH in a bulk solution and inside materials. Findings: The negative and positive values of Stern potential  for the positively and negatively charged surfaces were measured from the characteristic shifts of the EPR titration curves for the “slow-motional” NR located in the  material near-surface about those for a bulk solution. Stern layer thickness for mesoporous silicas  was determined from the near-surface electrical potential profile using a model of  practically cylindrical nanosized hydrated channels of the mesoporous silicas with channel diameters ranging from 2.3 to 8.1 nm. Conclusion & Significance: An unique technique for measuring the near-surface (Stern) potential as well as Stern layer thickness and surface charge  based on EPR of pH-sensitive nitroxides as spin probes and labels,  have been developed for a wide range of hydrated porous and nanostructured materials with a great potential for adsorption processes and heterogeneous catalysis.

  • Physical Chemistry: A Molecular Approach | Physical Chemistry of Macromolecules | Theoretical and Computational Chemistry | Chemical Physics | Femtochemistry
Location: Dublin, Ireland
Speaker
Biography:

Alex Boeglin is a researcher at Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg.

Abstract:

Today, metallopolymeric entities consisting of chains of metal ions interlinked with ambidentate ligands provide an attractive route towards so called “smart” materials capable of adjusting their physical properties in response to changes in environmental factors and/or to external stimuli.                The dynamic nature of the metal ligand bond in solution may readily be assessed through titration experiments based on linear optical properties and through vibrational spectroscopy.  However it is much more difficult to study the molecular motions persisting in the condensed phase although these are essential to the properties and performance of this class of emergent materials.

C2-symmetric bisoxazoline units have attracted much attention because they have been successfully used in enantioselective catalysis when suitably substituted at the 4-position of the oxazoline heterocyclic rings to make it a chiral centre.[i] When two isopropyl substituted oxazoline units are attached to a vinyl group, a bidentate monotopic ligand is achieved which shows a strong absorption band near 300nm but no circular dichroism in methanol. Optical activity is detected however as soon as transition metal ions are added to the solutions. It attests to the formation of complexes expressing their axial chirality in their electronic transitions. Moreover, after the slow evaporation of the solvent, liquid casted homonuclear homoleptic complexes are capable of generating detectable levels of sum-frequency (SFG) signals[ii] which are specific to isotropic chiral media, i.e. which lack inversion symmetry only at the molecular level.

In order to interpret these results, Density Functional Theory (DFT) based electronic structure calculations are performed on individual metal complexes to determine the possible arrangements of the ligands around the metal ions and evaluate their relative energies. Time dependent (TD-DFT) calculations are used to establish the relationships between conformational structure and optical properties.

Our results carry over to the related ditopic monomers containing bisoxazoline ligand units[iii]. But now, the formation of homoleptic homochiral species generates a chiral metallopolymer and lead to the formation of films of improved quality. The possibilities of optically active SFG based microscopy to study the formation of the metallopolymeric material obtained from chiral enantiopure components holds the promise of a sensitive technique where the optical expression of chirality can be used to probe self-assembling processes which may be relevant to other types of metallopolymers.

Speaker
Biography:

Roger Rousseau is awarded PhD in Inorganic Chemistry from The University of Michigan, USA in the 1995.  He holds a Master Degree in Inorganic Chemistry from The University of Michigan, USA in the 1994, followed by a Bachelor’s Degree in Chemistry from University of Windsor, Canada in the 1991. Currently, he is working as a Senior Staff Scientist for Pacific Northwest National Laboratory, Richland, Washington.  His research interests are focused on the application of quantum mechanical methods in simulations of the properties and reactivity of molecules, solids, and surfaces of relevance to catalysis for energy applications. Currently, Dr. Rousseau is working on the application and development of ab initio molecular dynamics methods to the study of heterogeneous and homogeneous catalysis reaction mechanisms. This includes participation in the Center on Molecular Electrocatalysis, an Energy Frontier Research Center, and PNNL's Institute for Integrated Catalysis.

Abstract:

Zeolite is one of promising solid acid catalysts for the conversion of renewable biomass-derived alcohols into fuels and chemicals.  Dehydration of alcohols to alkenes is a well-known prototypical acid catalyzed reaction, where confinement and entropic effects impact the rates of these reactions. For such conversions, HZSM-5 zeolite is commonly used as a platform for acid catalyzed reactions due to its strong acidity and enhancement of reaction rates due to confinement in pores.  In this talk, we present the structure and thermochemistry of ethanol adsorption on the Brønsted acid site of the HZMS-5 by means of ab inito molecular dynamics (AIMD) simulations directly compared with in-situ IR spectroscopy and thermochemical measurements on the same material. Simulations were performed using two different ethanol loadings (with/without deuterium substitution) at different temperatures (100 ≤ T ≤ 700). This enables us to take into account enthalpic and entropic effects caused by the dynamics of the motion of the reaction intermediates. AIMD simulations show that hydrogen transfer from the zeolite scaffold to ethanol occurs as temperature increases. In the simulations with higher ethanol loading, proton transfer occurs via relay between H-bonded ethanol molecules. Calculated projected vibrational density of states (VDOS) obtained from velocity autocorrelation function show a broad peak around 1600 cm-1 related to H-O-H bending mode which is also observed experimentally. We estimated entropy and enthalpy of adsorption using the computed VDSO along with a quasi-harmonic approximation, which shows good agreement with experimental measurement Conversely, the more commonly employed harmonic vibrations lead to free energy estimates that deviate from experiment substantially. Overall, this study exemplifies how enharmonic effects, as capture by AIMD, are critical for the quantitative modeling of the free energetics of zeolite-catalyzed processes.

Biography:

Chun Yuan Liu obtained his Ph.D degree in 2005, supervised by F. A. Cotton, at Texas A&M University. Currently, He is a full professor at Jinan University. His research has been focused on study of electronic coupling (EC) and electron transfer (ET) between two charge bearing sites by taking a molecular approach. He uses quadruply bonded Mo-Mo complex units as the electron donor (D) and acceptor (A) and a diverse of organic bridging ligand (B) to construct D-B-A experimental models, in which the transferring electron is identified to be the d electrons. Quantitative evaluations of the EC and ET properties are achieved with the physical chemical parameters (Hab, DG°, DG*, l, Ket…) derived from electrochemical and spectroscopic data under the semi-classical theories. In study of photoinduced electron transfer, it is found that the d*®d back electron transfer is quite different from the d®d ET reaction in the mixed-valence systems, thus, a quantum incoherent pathway is proposed.

Abstract:

Bridged dimolybdenum dimers, denoted as [Mo2]-bridge-[Mo2], are favorable model compounds for study of electronic coupling and electron transfer because of the unique electronic structure of the [Mo2] unit. The formation of the metal-metal multiple bond removes the d orbtal degeneracy, rendering the Mo2 unit a s2π4d2 electronic configuration. Therefore, as an electronic donor-bridge-acceptor system, the transferring electron is specified to be the d electrons and donor-acceptor electron transfer can be probed by the metal (d) to bridging ligand (π*) and bridging ligand (π) to metal (d) and vibronic (d) metal to metal (d) charge transfer absorptions in accordance with suppexchange theory. By varying the ancillary ligands and the bridging ligands, a diverse of complexes of this type have been synthesized and studied. The electronic coupling matrix elements (H) are evaluated according to the Mulliken-Hush and CNS theories, which give consistent results. The mixed-valence properties are discussed in terms of Robin-Day's scheme. System transition from Class II to Class III via Class II-III is examined in a series of four complexes with subtle structural differences. The d®d electron transfer kinetics in symmetrical as well as asymmetrical systems has been investigated, conforming well to the semi-classical two-state model and the Marcus-Hush theory. In study of the photoinduced electron transfer, we found the d*®d back electron transfer is faster than the process from the bridge to the Mo2 center by one order of magnitude, while in the latter case, the electron transfer distance is shorter but the electronic coupling is much stronger. This controversial electron transfer phenomenon is tentatively attributed to a quantum incoherent pathway.

Speaker
Biography:

Krzysztof Winkler obtained his M. Sc. (1982) and Ph. D. (1989) degrees in Chemistry from the Warsaw University, Poland. He was a postdoctoral fellow at the University of Saskatchewan, Saskatoon (1989-1991) and University of California, Davis (1995-1997). He is currently a professor in the Institute of Chemistry, University of Bialystok, Poland. He served four terms as Head of this Institute (2004-2017). His research interests include kinetics of electrochemical processes, electrodeposition and properties of low-dimensional crystals,  the synthesis, properties and application of fullerene-based polymers.

Abstract:

In coordination fullerene polymers, fullerene moieties are covalently bonded to transition metal atoms or their complexes to form a polymeric network. The polymer of fullerene C60 and palladium, poly(C60Pd3), was the most intensively investigated. This polymer can be synthesized electrochemically or chemically. The electrochemical synthesis results in the formation of thin and uniform film on the electrode surface. The film is electrochemically active at negative potentials due to the fullerene cages reduction. During switching between neutral and reduced state, the polymeric film is doped with supporting electrolyte cations. Such transition also results in sharp increase of the film conductivity. The conductivity of poly(C60Pd3) thin films was experimentally investigated with interdigitated array electrodes. The poly(C60Pd3) doping level and, therefore, charge carriers density depends on the size of counter-ions incorporated into polymeric structure during its reduction. The negative polaron-type carriers generated during the film reduction are responsible for film conductivity. The charge propagation through the polymeric film can be quantitatively described be electron-hopping model. The specific conductivity of poly(C60Pd3) and electron diffusion coefficient are in the same order of magnitude as these values reported for typical p-doped conducting polymers. The conductivity properties of the composite of poly(C60Pd3) polymer and palladium nanoparticles were also investigated. Metallic nanoparticles participate in the charge transport within the film also in the potential range of the polymer neutral state. Therefore poly(C60Pd3)/Pd composite exhibits large potential window of good conductivity. The structure and conducting properties of poly(C60Pd3) polymers were also predicted applying DFT calculations. The isolated negative polarons are the preferred electronic states for reduced polymers.

George Fytas

Max Planck Institute for Polymer Research, Germany

Title: Soft based hypersonic phononics
Speaker
Biography:

Born in Athens, Greece, George Fytas is professor of Physical Chemistry at the Department of Materials Science & Technology of the University of Crete and External Member of the Max Planck Society since 1998. Fytas holds a PhD in Physical Chemistry of the Technical University of Hannover, Germany, performed his postdoc research in SUNY at Stony Brook in USA and received his habilitation from the University of Bielefeld in Germany. He has received a Humboldt Senior Research Award (2002), became a Fellow of the American Physical Society (2004), is Adjunct Professor at the University of Akron (2013) and received an ERC Adv.Grant for phononics (2015).

Abstract:

Phononic structures (composite materials in which a periodic distribution of elastic parameters facilitates control of the propagation of phonons, hold the promise to enable transformative material technologies in areas ranging from acoustic and thermal cloaking to thermoelectric devices. This requires strategies to deliberately ‘engineer’ the phononic band structure of materials in the frequency range of interest. Phononics, the acoustic equivalents of the photonics, are controlled by a larger number of material parameters, as phonon cannot propagate in vacuum. The study of hypersonic phononics (hPnC) imposes substantial demand on fabrication and characterization techniques. Colloid and polymer science offer methods to create novel materials that possess periodic variations of density and elastic properties at length scales commensurate with the wave length of hypersonic phonons and hence visible photons. The key quantity is the dispersion ω(q) of high frequency (GHz) acoustic excitations with wave vector q which is measured by the noninvasive high resolution Brillouin light scattering. The approach involves the exploitation of Bragg-type bandgaps (BGs) that result from the destructive interference of waves in periodic media. However, the sensitivity of BG formation to structural disorder limits the application of self-assembly methods that are susceptible to defect formation. Hybridization gaps (HG), originating from the anti-crossing between local resonant and propagating modes, are robust to structural disorder and occur at wavelengths much larger than the size of the resonant unit. Here, examples based on hierarchical structures will be highlighted: (i) 1D-hPnC to acquire comprehensive understanding, while the incorporation of defects holds a wealth of opportunities to engineer ω(q).1,2 (ii) In colloid based phononics, ω(q)  has revealed both types of band gabs. 3,4 (iii) particle brush materials with controlled architecture of the grafted chains enable a new strategy to realize HG’s 5 (iv) Hierarchically nanostructured matter can involve unprecedented phonon phono propagation mechanisms .6

Biography:

Toshiaki Matsubara is working as a Professor in Department of Chemistry, Faculty of Science, at Kanagawa University, Japan.

Abstract:

I will introduce two subjects1,2 we have examined by the combination of quantum mechanical and molecular dynamics methods

I.    It has been known that the nucleophilic substitution at the Si atom,

SiH3Cl + Cl*- → SiH3Cl* +    Cl-, proceeds by two steps with the inversion or retention of the configuration passing through an intermediate with the trigonal bipyramid (TBP) structure (Figure 1), although the conventional SN2 reaction at the C atom proceeds by one step with the inversion of the configuration passing through a transition state with the TBP structure. We followed by the QM method all the possible paths and found that TBPcis produced with a high probability  is  readily  transformed  to  the  energetically  more stable TBPtrans. In order to obtain more information concerning the trajectory of Cl- on the dissociation from TBPtrans, which we cannot clarify on the basis of the energy profile determined by the QM method, we conducted the MD simulations with and without the water solvent. The QM-MD3 simulations without the water solvent revealed that the dissociation of Cl- from TBPtrans occurs without passing through TBPcis. The ONIOM-MD3 simulations with the water solvent further suggested that the thermal fluctuation of the water solvent significantly affects the oscillation of the kinetic and potential energies of the substrate to facilitate the isomerization of the TBP intermediate from the cis form to the trans form and the subsequent dissociation of Cl- from TBPtrans.

II. Germanone R2Ge=O have not been isolated until recently, because it easily polymerizes due to its unstability. However, Tamao et al. recently succeeded to isolate the germanone (Eind)2Ge=O by the incorporation of bulky substituents called Eind. The isolated (Eind)2Ge=O is very reactive and the reactions that do not proceed in the case of ketone easily proceed in the case of germanone. For example, the σ bond of water adds to the Ge=O of germanone to form the germanediol at room temperature. In this study, we examine the mechanism of the σ bond cleavage of the substrate on the Ge=O bond. In the case of H2O, the QM calculations showed that the H2O coordinates to the Ge before the σ bond cleavage (Figure 2) and this coordination induces a heterolytic σ bond cleavage. We further performed the QM-MD3 simulations and found that the kinetic energy concentrates on the coordinated H2O oxygen to strongly oscillate the coordinate bond. This oscillation further enlarges just before the O-H σ bond cleavage. The kinetic energy of this oscillation would be transmitted to the normal  mode  of  the  O-H  bond  breaking. Thus, the coordination and the vibration of the  H2O  oxygen was  thought o be an important driving force of the O-H σ bond cleavage.

Speaker
Biography:

Emanuele Curotto was born and raised in Italy until the age of 24. In 1988 he immigrated to the United States, completed his Bachelor of Science at the University of Massachusetts Lowell, earned a Doctorate from Yale University in 1996 under the direction of Dr. J. Cross,  and was a postdoctoral fellow at the University of Rhode Island under the direction of Dr. D. L. Freeman. He was hired at Arcadia University (formerly Beaver College) in 1998 where he currently serves as Professor and Department chair. 

Abstract:

Over the past two decades, our group at Arcadia University and the Mella group at the Universita` degli Studi dell'insubria, have been closely collaborating in the development and implementation of quantum Monte Carlo methods, primarily to estimate nuclear quantum effects in condensed matter and clusters.  The most recent advances include the formal development of Path Integral and Diffusion Monte Carlo methods that permit enhanced convergence when rigid constraints are included in simulations, the introduction of Smart – Darting – like techniques to enhance the sampling of the ground state density in extremely frustrated systems, and the exploration of the mathematical property of the Langevin equation in manifolds with boundaries and gradient torsion associated with nodal surfaces of excited states.  Application examples include the determination of coupling effects on the ground state of gas phase molecules between rotation and torsional degrees of freedom, the determination of the ground state energy and wavefunctions of lithium-ion Stockmayer clusters, the enhancement of hydrogen isotopic separation offered by the surface of ammonia clusters, the Ring Polymer Molecular Dynamics from the Brownian Bridge representation of the Path Integral, and the simulation of multi-electronic states in the Kustaanheimo-Stiefel Space by Diffusion Monte Carlo. 

The capped pentagonal bipyramid global minimum of the 5-D PES [J. Chem. Phys. 129,. 094304 (2008). ] of (H2)10.

Fabienne Berthier

Paris-Sud University, CNRS, FRANCE

Title: What is hidden behind a phase diagram?
Speaker
Biography:

Fabienne Berthier has her expertise in the modelling the thermodynamical properties of alloys to predict phase diagrams. She has developed a methodology that mix a rigid lattice Ising model with off lattice Monte Carlo simulations. This mixed approach is very efficient to predict and analyze the interfacial segregation as for example at grain boundaries, surfaces and nanoparticles. She has also an expertise in growth kinetics and ageing kinetics.

Abstract:

The thermodynamics of binary alloys is still far from being well understood despite numerous studies, in particular when the two constituents have very different atomic volumes. That is the case for the Au-Ni and Ag-Cu alloys that tend to phase separate and possess a large size mismatch. The phase diagrams of the two systems are characterized by a large miscibility gap. This apparent simplicity is, nevertheless, undermined by studies on the local order (short-range-order SRO). The ordering SRO observed experimentally is agreement with the phase diagram for Ag-Cu whereas it remains controversial for Au-Ni.

We present a novel energetic model that takes into account atomistic relaxations to describe the thermodynamic properties of binary alloys . It involves of the calculation of site energies in a relaxed random solid solution as a function of the local composition and of the nominal concentration. The numerical results are obtained using N-body interatomic potentials derived on the second moment approximation (SMA) of the tight-binding scheme. This new model allows us to determine the effective pair interactions (EPI) that drive the SRO and to evaluate their contribution to the mixing enthalpy, as well as that of related to the lattice mismatch between the components.

We apply this formalism to the Au-Ni and Ag-Cu alloys. Monte Carlo (MC) simulations on rigid lattice using this energetic model lead to phase diagrams that are in remarkable agreement with that obtained with SMA-MC simulations and the experimental ones. We show that the phase separation is mainly driven by the elastic contribution for Au-Ni and by the EPI’s contribution for Ag-Cu. Furthermore for Au-Ni, SRO which are related to the EPIs, display a sign change as a function of the concentration.

Figure 1: Evolution as a function of  of the mixing enthalpy  (black line) and of its two contributions  (red line) and  (blue line) for  (left) and  (right).

Speaker
Biography:

Dr. V.-A. Glezakou is a computational chemist with over 20 years of experience in atomistic simulations, with particular emphasis in transition metals chemistry and condensed phase systems relevant to carbon capture an conversion, catalysis and materials properties. The focus of recent research is in the structure, vibrational spectroscopy and structure/activity correlations in a diverse ensemble of problems such as catalytic activity of metal clusters and oxide supports, transformative solvents for post-combustion carbon dioxide separations, mechanistic studies of MOF nucleation, solvatochromic effects in surface-supported chromophores. She is co-supervising a group of about 10 staff and post-docs that are tasked with the integration of fundamental and applied studies that help accelerate timesensitive technologies.

Abstract:

CO2 capture from power plant exhaust is a complex problem that requires the capture and removal of massive quantities of gases. Solvent technologies for CO2 capture and conversion have become one of the most promising solutions with aqueous amines being one of the industrial standards. However, their high regeneration costs render them prohibitive for many of the large-scale applications in power generation. My presentation will outline the computational approach used toward the deliberate design of single-molecule CO2-bidining transformational solvents. These types of solvents constitute an attractive alternative to the water-based solvents, but are hampered by  exponentially increasing viscosities at high CO2 saturation. Using state-of-the-art computational methods, like enhanced sampling methods for reaction free energetics in explicit solvent models using ab initio molecular dynamics, we describe the key structural parameters that allowed us to create reduced models for fast screening of solvent libraries. This approach led to tangible hypotheses as to the synthetic protocols that have already identified candidate molecules with appreciable viscosity reductions at target loading levels.

 

Speaker
Biography:

Prof. Ivan Štich has his current scientific interests in atomic-scale imaging and nanomanipulation with surface probe techniques, nanotribology, and 2D materials and their functionalization. In addition to mean field electronic structure techniques he also develops and applies ultra-accurate Quantum Monte Carlo methods for fermionic systems.

Abstract:

Transition metal organometalics has recently attracted much attention due to its potential for applications in catalysis, molecular recognition, high-density storage, quantum computing, and spintronics. Despite these applications, reliable theoretical and experimental knowledge of energetics, dissociation energy, spin multiplicity, spin gaps, etc. of these systems is still missing. Therefore we have performed very accurate fixed-node quantum Monte Carlo (QMC) calculations [1] with the quest to elucidate electronic, magnetic, and atomic structure of these systems in both neutral and charged states and thus to provide ultimate answers to the open questions.

For half-sandwich systems (vanadium-benzene and cobalt-benzene) [2, 3], which are important model systems for magnetic adatoms on graphene, we find results qualitatively different from DFT predictions for both spin ground-states as well as for fragmentation energies. Perhaps surprisingly, we conclude that also some experimental results may be strongly biased.

We have also studied full-sandwich vanadium-benzene multi-decker clusters, VnBzn+1, n = 1 - 3 in both neutral [4] and charged states [5]. The most important prospective applications of these and related systems are in spintronics as spin filters. Use as spin filters requires them to be half-metal ferromagnets, in order to feature a metallic gap for the minority-spin electrons and semiconducting gap for the majority-spin electrons. We find that, while magnetic structure of these systems is consistent with ferromagnetic coupling, their electronic structure is not consistent with half-metallic behavior as previously assumed, but rather these systems are ferromagnetic insulators with large and broadly similar ­-/¯-spin gaps, implying thus a limited potential of these and related materials for spintronics applications unless they are further modified or functionalized.

Figure 1. Model of vanadium benzene full-sandwich molecules featuring ferromagnetically coupled vanadium atoms. Right: ­-/¯-spin gaps for vanadium-benzene full sandwich structures in DFT and QMC treatments.

Speaker
Biography:

Richard Tuckett obtained his PhD in near-infrared spectroscopy from the University of Cambridge in 1979.  He first worked in electronic fluorescence spectroscopy of free radicals and molecular cations, often using supersonic beams and non-resonant electron excitation.  From the late 1980s, he started using tunable vacuum-ultraviolet photon excitation from a synchrotron as a resonant ionisation source.  He also developed an interest in threshold photoelectron spectroscopy and related coincidence techniques, particularly threshold photoelectron photoion coincidence studies.  Experiments have been performed with three sources: Daresbury UK, Bessy I Germany, and now the Swiss Light Source.  During his career, he has taken sabbatical leave at Stanford University (1993) and ETH Zurich (2006).

Abstract:

The history and evolution of molecular threshold photoelectron spectroscopy and threshold photoelectron photoion coincidence spectroscopy (TPEPICO) in the gas phase over the last fifty years will be reviewed.  Emphasis will be placed on instrumentation and the extraction of dynamical information about energy selected ion dissociation, not on the detailed spectroscopy of certain molecules.  Three important advances have greatly expanded the power of the technique, and permitted its implementation in modern synchrotron radiation beamlines.  (a) The use of velocity focusing of threshold electrons onto an imaging detector in the 1990s simultaneously improved the sensitivity and electron energy resolution, and also facilitated the subtraction of hot electron background in both threshold electron spectroscopy and TPEPICO studies.  (b) The development of multi-start multi-stop collection detectors for both electrons and ions in the 2000s permitted the use of the full intensity of modern synchrotron radiation thereby greatly improving the signal-to-noise ratio.  (c) Finally, recent developments involving imaging electrons in a range of energies as well as ions onto separate position-sensitive detectors has further improved the collection sensitivity, so that low density samples found in a variety of studies can be investigated.   As a result, photoelectron photoion coincidence spectroscopy is now well positioned to address a range of challenging problems that include the quantitative determination of compositions of isomer mixtures, the detection and spectroscopy of free radicals produced in pyrolysis or discharge sources as well as in combustion studies.

 

Speaker
Biography:

Robert F. Tournier is born in 1934 and is named Emeritus Research Director at CNRS Grenoble in 2000. His group showed the appearance of magnetic moments in clusters of transition atoms and the existence of scaling laws for diluted spin glasses. The magnetic susceptibility of isolated impurities submitted to Kondo effect was separated from that of magnetic clusters. The disappearance of Kondo effect by antiparallel coupling of nuclear and electronic spins ½, the local spin fluctuations and electronic moments induced by nuclear moments in Praseodymium Van Vleck compounds were also discovered. The coexistence between superconductivity and ferromagnetism was studied or discovered in few compounds. Magnetic texturing of permanent magnets and high Tc superconductors by solidification in a high magnetic field and water levitation were obtained. He was rewarded by distinctions: Prix Ancel 1970 (French Society of Physics); Grand Prix Jaffe 1985 (Sciences Academy.); Lifetime achievements 2012 (Magneto-science Society of Japan).

Abstract:

The classical nucleation equation fails to predict the glass phases, the liquid-to-liquid phase transitions (LLPT), Lindemann’s constant, the presence of intrinsic growth nuclei above Tm inducing magnetic texturing by cooling magnetic melts in high magnetic fields, and the first-order glass transitions of liquid helium under pressure. These problems are solved adding in (1) an enthalpy saving e×DHm associated with the formation of spherical growth nuclei (superclusters) having the same melting temperature Tm and melting enthalpy DHm per mole whatever their radius R is:

where  is a numerical coefficient equal to els or egs or Delg=(els-egs) with the indexes l for liquid, s for solid and g for glass phases, q =(T-Tm)/Tm and q0 is q0l or q0g. The glass transition is viewed as a LLPT from Phase 1 above Tg to Phase 2 below Tg. els×DHm is reduced at the glass transition with els replaced by egs and q0m by qog, els and egs being the enthalpy saving maximum coefficients associated with the homogeneous nucleation of nuclei inducing crystallization. The enthalpy change at Tg giving rise to the glass phase obeys (1) with e replaced by Delg. All thermodynamic properties are calculated when Tg, els=els0 at Tm and q0l are known. Phase 3 is relaxing in Phase 2. An enthalpy excess, due to quenching the melt or to vapor deposition, can induce sharp transitions to Phase 3. Two homogeneous nucleation temperatures q =e above Tm and q =(e-2)/3 below Tm are expected  minimizing the surface energy. Values of e have been obtained in pure liquid elements, strong and fragile glass-forming melts. In pure liquid elements, the smallest value els0=0.217 leads to Lindemann’s constant equal to 0.103 at Tm. Delg, els and egs are used to predict LLPT between Phase 1 and Phase 2 above and below Tm even in water.

Speaker
Biography:

Sandra Luber received her MSc and PhD degree from ETH Zurich in 2007 and 2009, respectively. After postdoctoral studies at Biozentrum of the University of Basel (2010) and Yale University (2010-2011), she joined BASF SE in 2012. Afterwards she became project group leader at the University of Zurich. The habilitation thesis was finished in 2016 and she is currently an SNSF professor at the University of Zurich. Awards include the ETH medal for an outstanding PhD thesis, the IBM Research Prize for Computer Modelling and Simulations in Chemistry, Biology, and Materials Science, and the Clara Immerwahr Award 2017.

Abstract:

Knowledge about properties of liquids is extremely helpful for the analysis of molecular structures and interactions. Moreover, it is a valuable source of information for the characterization of dynamic processes and facilitates the interpretation of experimental data. Calculations provide additional insight allowing the targeted study of specific structures. In this way, it is possible to quantify the contributions of, e.g., solute and solvent molecules or adsorbates on solids.

We present innovative methods for the calculation of spectroscopic and local properties for periodic systems such as liquids, which can efficiently be employed in density functional theory-based molecular dynamics. Moreover, computationally efficient approaches for the calculation of Raman and Sum Frequency Generation spectroscopy have been developed as well as the first method for Raman optical activity spectroscopy from ab initio molecular dynamics. Recently studied systems include a gas-semiconductor interface as well as ionic liquids.

Speaker
Biography:

Tatsuhiko Ohto is an assistant professor at Osaka University, Osaka, Japan. He received his PhD degree from The University of Tokyo in 2013. During his PhD course, he spent 5 months as a visiting student at the Max Planck Institute for Polymer Research, Mainz, Germany. After postdoctoral research at the Advanced Institute of Science and Technology, Tsukuba, Japan, he joined Osaka University. His research interest is theoretical modeling, primarily based on first-principles calculations, of the structure and dynamics of molecules at interfaces and the electron transport of metal–molecule–metal systems.

Abstract:

Understanding aqueous interfaces at the molecular level is not only fundamentally important, but also highly relevant for a variety of disciplines. For instance, electrode–water interfaces are relevant for electrochemistry, as are mineral–water interfaces for geochemistry and air–water interfaces for environmental chemistry; lipid–water interfaces constitute the boundaries of the cell membrane, and are thus relevant for biochemistry. One of the major challenges in these fields is to link macroscopic properties such as interfacial reactivity, solubility, and permeability as well as macroscopic thermodynamic and spectroscopic observables to the structure, structural changes, and dynamics of molecules at these interfaces. Simulations, by themselves, or in conjunction with appropriate experiments, can provide such molecular-level insights into aqueous interfaces. We study aqueous interfaces, by assessing computations of the sum-frequency generation (SFG) spectra, which selectively detect the interfacial molecules, at aqueous interfaces. To avoid bias in the computational results and interpretation originating from the choices of the details of FF models, applying a parameter-free ab initio molecular dynamics (AIMD) simulation technique to the SFG calculation seems to be a promising route. However, the huge computational cost required for AIMD simulation has prohibited the widespread use of AIMD simulations for computing the SFG spectra. We have recently presented an efficient calculation algorithm for computing the SFG spectra of the water O–H stretch mode based on the surface-specific velocity–velocity correlation function, by separating degrees of freedom of the nuclei from solvation effects such as the induced dipole and polarizability. This methodology has been applied to the fundamental water-air, water-lipid, and aqueous solution-air interfaces. We are going to extend our method to solid-liquid interfaces.

Figure: Trymethylamine-N-oxide solution-air interface.

Speaker
Biography:

Isa Degirmenci has his expertise in structure-reactivity relationships in the free radical polymerization reactions. His investigations combine the understanding the structure properties of radical species and monomers with application of quantum chemical tools. His recent studies have simply explained the extraordinary reactivity and stability behavior of sulfur-centred radicals. These findings can be considered as paving the way for further utilizing recently emerged the thiol-ene and thiol-yne polymerization reactions and also for further benefitting from self-healing reaction mechanisms of polymeric materials.

Abstract:

Recently, there has been growing interest in both the thiol-ene (Scheme 1) and thiol-yne sister reactions in various application areas from polymer field to bioconjugative materials due to the extraordinary advantages of these reaction techniques in, for example, forming uniform polymer networks with narrow Tg values and low shrinkage stress. The most outstanding feature of these reactions is combination of the advantages of both step growth and chain growth polymerization reactions. Another attractive subject is self-healing polymeric materials that have been brand-new of interest in polymer science. Some of these materials utilize trithiocarbonate or thiuram disulfide units in the polymer structure which allows healable backbone of polymer chain. It is well known that the sulfur-centred radicals play a vital role in these thiol reactions or self-healing processes. To better understand the structure-reactivity trends of these extraordinary radicals, we have used computational chemistry (at the G3(MP2)-RAD//MP2/6-31G(d) level of theory) to study the highly reactive alkyl thiyl radical addition reaction to the C=C and S=C double bonds of various compounds. In addition to this, the high stability of the sulfur-centred radicals has been extensively studied to elaborate controversial behavior of these radical species. We find that the high SOMO energy of the radicals has the ability to undergo resonance interactions with π* of the substrate and this allows formation of stabilized transition state structure in radical addition reactions. The same effect is account for enormous stability of sulfur-centred radicals which are more effectively conjugated with heavier lone-pair donor and π-acceptor substituents than carbon-centred radical analogues.

Speaker
Biography:

Richard M. W. Wong received his Ph.D. degree from Australian National University (1989). Subsequently, he held postdoctoral position at IBM Kingston and Yale University. In 1992, he took up an Australian Research Fellowship, hosted in University of Queensland. He joined the National University of Singapore in 1997 and is currently a full professor and head of department. He was the recipient of Fukui Award recently on his outstanding work in theoretical and computational chemistry. Prof. Wong has published about 200 scientific publications, which received over 9000 citations and H-index of 42. His research interests include application of computational quantum chemistry to a range of chemical problems, reactive intermediates, catalysis, materials design, chemical sensors, weak intermolecular interactions and drug design.

Abstract:

Obtaining a detailed insight into the mechanism of the protective action of various organic corrosion inhibitors on mild steel corrosion has remained an active area of research over the years. The use of computational chemistry as a tool in this aspect have greatly enhanced the prediction of the inhibition efficiencies of these inhibitors based on their electronic and molecular properties and reactivity indices, which are subsequently validated by experimental measurements. In the present study, we investigated the corrosion inhibition efficiency of mild steel in 1.0 M HCl of the following compounds; imidazole (Imz), 2-bromo-1H-imidazole (2-Br-Imz), 2-chloro-1H-imidazole (2-Cl-Imz), 2-iodo-1H-imidazole (2-I-Imz) and 4-phenyl imidazole (4-Ph-Imz). Density functional theory (DFT) calculations showed that the inhibitor molecules dissociate to form a network of protective film on the iron surface. The equilibrium adsorption energies obtained from DFT calculations decreases in the order 2-I-Imz > 4-Ph-Imz > 2-Br-Imz > Imz > 2-Cl-Imz. Electrochemical studies of the two extreme cases showed that 2-I-Imz exhibited the best inhibition efficiency of 82.95 % at 10 mM concentration acting as anodic-type inhibitor while 2-Cl-Imz exhibited an efficiency of 50.70 % at the same concentration acting as cathodic-type inhibitor. Both inhibitors were found to fit the Langmuir adsorption isotherm with Gibbs free energy of adsorptions -27.34 KJ/mol and -25.24 KJ/mol at 25 oC for 2-I-Imz and 2-Cl-Imz respectively. SEM of the steel samples after immersion in the inhibitors for 24 h revealed a significant formation of pits on the 2-Cl-Imz sample possibly due to chloride attack, and the absence of such in the 2-I-Imz sample indicating its ability to form a protective film. XPS analysis confirmed the adsorption of the inhibitor molecules on the metal surface from the functional group analysis of the peaks obtained. AFM analysis showed a decrease in surface roughness of the 2-I-Imz sample as compared to the 2-Cl-Imz, indicative of a better adsorption and consequent inhibition efficiency observed of both inhibitor molecules.

Speaker
Biography:

Anup K. Gangopadhyay is working as a Research Scientist in Washington University in St. Louis, USA.

Abstract:

Glasses are traditionally classified as “fragile” or “strong”, depending on the rates of change of dynamical properties (viscosity, diffusion coefficient) with temperature near the glass-transition temperature. It will be shown that the temperature dependence of viscosity far above the liquidus is an equally good measure of fragility. From the measurements of liquid structures of a large number of metallic glass-forming liquids using the electrostatic levitation (ESL) technique, combined with synchrotron x-rays, it will be demonstrated that the rates of structural changes of equilibrium and supercooled (metastable liquid below the liquidus) liquids with temperature are intimately connected with the liquid/glass fragilities. A strong connection between fragilities and average cohesive energies for metallic liquids will also be demonstrated.

Manabendra Sarma

Indian Institute of Technology Guwahati, India

Title: Low energy electrons induced damage to selected DNA fragments
Speaker
Biography:

Dr. Manabendra Sarma received his B.Sc. and M.Sc. degrees in the year 2000 and 2002 respectively from Goalpara College (A College Affiliated to Gauhati University) and Indian Institute of Technology Guwahati, Assam, India. After getting his M.Sc. degree, he moved to Indian Institute of Technology Bombay, Mumbai, India in 2002 to pursue his Ph.D. work under Professor Manoj K. Mishra. He obtained his Ph.D. degree in 2008 and subsequently joined in the Department of Chemistry at Indian Institute of Technology Guwahati, Assam, India as a senior lecturer in the same year. In the year 2011, he received the prestigious BOYSCAST Fellowship of India to work with Professor Lorenz S. Cederbaum of University of Heidelberg, Germany for a year. Dr. Sarma’s current research interests include development of new theoretical approaches to laser assisted control of chemical reactions and resonances in electron-molecule scattering. Currently Dr. Sarma is an associate professor in Chemistry at Indian Institute of Technology Guwahati, Assam, India.

Abstract:

We have theoretically and computationally investigated the mechanism of low energy electron (LEE) induced DNA damages such as single strand breaks (SSBs) and glycosidic bond cleavage in some selected DNA fragments (Fig. 1) viz., 2¢-deoxycytidine-3¢-monophosphate (3¢-dCMPH) [Fig. 1(a)], 2¢-deoxycytidine-5¢-monophosphate (5¢-dCMPH) [Fig. 1(b)] and sugar-phosphate-sugar (SPS) [Fig. 1(c)]. In this regard, we have used electronic structure theory and our newly implemented local complex potential based time dependent wave packet (LCP-TDWP) approach. Results from our calculations show that in 3¢-dCMPH and 5¢-dCMPH DNA fragments SSB predicted near 1 eV whereas in SPS moiety it appears around 0.6 eV. Further, in case of SPS moiety there are two dissociation channels namely 3¢ C-O and 5¢ C-O bond lesions. Our calculations show that the activation energy barrier for 5¢ C-O bond dissociation is less than of 3¢ C-O bond dissociation pathway. It has also been found that the metastable anion formed after electron attachment to SPS moiety is more long lived (~40-55 fs) than that to 3¢-dCMPH and 5¢-dCMPH fragments (~18-20 fs). On the other hand, the glycosidic bond cleavage in 3¢-dCMPH moiety [Fig. 1(d)] requires higher activation energy than of the SSB in the same fragment and thus least preferred channel compared to SSB.

      (a)                             (b)                          (c)                       (d)

Figure 1: Some of the selected DNA fragments. For each fragment bond susceptible for cleavage is marked with an arrow.

Speaker
Biography:

Dafna Knani is a senior Lecturer at the department of Biotechnology Engineering, ORT Braude College. She is an organic polymer chemist, graduated from the chemistry faculty, Technion- Israel Institute of Technology. In the past, she worked for Surgical bio-polymeric materials start-up company as a research polymer chemist (developing adhesives for hard tissues) and as a research chemist and project leader at Israel Chemicals Ltd. (ICL), IMI-Institute for R&D. Her current research focuses on molecular modeling of materials and biomaterials. Some of her research topics are simulation of systems used for controlled drug release and tissue engineering and computational design of polymer additives.  Since 2014 she serves as the head of MSc program in biotechnology.

Abstract:

The organic gelator 1,3(R):2,4(S)-dibenzylidene-D-sorbitol (DBS) self-organizes to form a 3-D network at relatively low concentrations in a variety of nonpolar organic solvents and polymer melt. DBS could be transformed into a hydrogelator by introduction of hydrophilic groups, which facilitate its self-assembly in aqueous medium. In this work, we have investigated the hydrogelators DBS-COOH and DBS-CONHNH2 and the organogelator DBS by molecular modeling. We have used quantum mechanics (QM) to elucidate the preferred geometry of one molecule and a dimer of each of the gelators, and molecular dynamics (MD) to simulate the pure gelators and their mixtures with water.

The results of the simulation indicate that the interaction between DBS-COOH molecules is the strongest of the three and its water compatibility is the highest. Therefore, DBS-COOH seems to be a better hydrogelator than DBS-CONHNH2 and DBS.  Intermolecular H-bonding interactions are formed between DBS, DBS-COOH and DBS-CONHNH2 molecules as pure substances, and they dramatically decrease in the presence of water. In contrast, the intramolecular interactions increase in water. This result indicate that in aqueous environment the molecular structure tend to be more rigid and fixed in the preferred conformation. The most significant intramolecular interaction is formed between O3 Acetal and H-O6 groups. Due to the H-bonds, DBS, DBS-COOH and DBS-CONHNH2 molecules form a rigid structure similar to liquid crystal forming molecules, which might explain their tendency to create nanofibrils. It was found that the aromatic rings do not contribute significantly to the inter-and intra-molecular interactions. Their main role is probably to stiffen the molecular structure.

Figure 1: DBS, DBS-COOH and DBS-CONHNH2 molecular structure.

Speaker
Biography:

 Dr. Alok Satpathy has a passion for research in basic sciences. He has been pursuing theoretical research for more than two decades in the field of soft condensed matter physics, in spite of limited resources and facilities. Being an expert in the Statistical -Mechanical Model studies of structure, thermodynamics and transport properties of liquids, metallic glasses and amorphous substances such as molten metals, alloys and ionic (full, partial and complex) liquids, he has developed generalized theoretical models for investigating structural and thermodynamic properties of ionic liquids having mixtures of arbitrary charge and size

His awarded (1991, Jadavpur University, Kolkata) PhD (science) thesis- “STATISTICAL MECHANICS OF SOME PARTIALY ORDEED SYSTEMS” was commented as “A work of very high scientific level” with an excellent thesis report from MAX-PLANK-INSTITUT, Germany.

Dr.Satpathy has been popularizing science and its philosophy in society through active involvements in innumerable seminars, talks and other activities spanning throughout his career.

Abstract:

 The anomalous properties of liquid alloys of alkali metals with group III, IV,V and VI elements ( post transition  metals or semi metals), particularly alkali metals and group-IV(usually Pb and Sn) alloys at and around the stoichiometric  compositions have tempted internationally to thrust research works in these materials for the last three and half decades. The observed peculiar properties i.e. departure from ideality in the structure, thermodynamic and other related properties in these systems have been attempted to explain with the hypothesis of the existence of polyanions i.e. zintl ions such as (Pb4)4- , (Sn4)4-and (Te2)2-etc. But, the existence of these ions or complex compounds is not experimentally confirmed and some of the observed phenomena are also self contradictory to the basis of zintl principle. Hence, concluded as paradox by many authors. So, a new bonding scheme of loose overlapping of the atomic orbitals is introduced to tackle this paradox. Hence, a significant amount of effective charge transfer takes place between the atoms in the stoichiometric compositions. The chemical short range order (CSRO) in these alloys has been explained by coulomb interaction in lieu of zintl hypothesis. The generalized models for structure and thermodynamics of charged –hard-spheres mixture of arbitrary charge and size has been developed through my sustain efforts of decades’ research. These models are employed successfully to evaluate the structure and thermodynamic properties i.e., entropies and entropies of mixing etc., treating the samples as partially charge transferred systems. Thus, internationally proclaimed paradox has been resolved. Some of the excellent research outcomes, achievements of my decades’ struggle along with the future plan would be delivered in this invited speech.

Speaker
Biography:

Alexei Buchachenko is the professor of Skolkovo Institute of Science and Technology in Moscow, Russia and also holds part-time professor position at the Department of Chemistry of Moscow State University. His research interests are connected with the theoretical studies of structure, spectroscopy and dynamics of small molecules, recently with applications atomic, ionic and molecular systems at low temperatures.

Abstract:

Matrix isolation spectroscopy of atomic and small molecular species regularly and reproducibly reveals the existence of distinct trapping sites, sometimes undergoing reversible and irreversible interconversion processes upon heating or irradiation, see, e.g., refs.1-3. While the modeling of trapping site structures as the minima on the potential energy surface is a mature task [1], assessment of thermodynamic stability implies the consideration of ensembles of structures thus requiring special efforts. Recently, we have proposed the model compatible with the thermodynamic phase stability analysis [2]. Assuming a crystalline matrix, the model, first, compromises its local distortions by embedded host and long-range crystal order. Second, the correction to atomization energy allows one to consider the structures of distinct nature – insertions, substitutions and vacancy formations – at the same energy scale. Resulting dependence of the energy on the number of host atoms removed from the system makes it possible to use the convex hull concept [4] to identify thermodynamically stable site structures. The figure exemplifies such dependences for Mn atom trapped in Ar, Kr and Xe, as calculated using the ab initio-based pairwise interaction potentials [5]. It illustrates stabilization of the single substitution (SS) site and destabilization of the tetravacancy (TV) one with the size of host atom, in agreement with recent spectroscopic data [3]. Application of the model to Mn2 molecule has revealed that the matrix accommodates this weakly-bound dimer “per atom”, merging stable atomic SS and TV structures within the single unit cell. These sites are discernible by vibrational frequencies and spin-spin coupling parameters. Other examples of trapped species are also considered. Identification of the thermodynamically stable trapping site structures provides the grounds for interpreting slow heat- and light-induced processes in cryogenic matrices and facilitates accurate spectroscopic and dynamical simulations of the matrix isolated species.

The contribution by D.S. Bezrukov, as well as the financial support by Russian Science Foundation (#17-13-01466), is gratefully acknowledged.

Biography:

Rostislav Gerasimov has his expertise in radioscopy of liquids, solids and nondestructive control of construction materials. His universal non-destructive testing method in microwave range is based on comparing the research object to the reference pattern. Years of research and huge data on considered substances and objects allows to research dynamics of the processes.

Abstract:

The proposed new method based on the spectra of radio wave radiation of the microwave range wideband scanning receiver. It is experimentally proved that this method has a high accuracy in the determination of the frequency spectrum. This allows to reach a sensitivity of 5-6 Hz/nm. The obtained spectra are analyzed for the particular program hardware-software complex. Practice has shown that the proposed method allows not only to detect the difference of the substances qualitative composition and concentration, but also to determine the presence of heavy and superheavy hydrogen isotopes in water. The method for determining the presence of substances in nanoscopic amounts is based on the registration of radio-wave emission spectra in the microwave region using a scanning wideband receiver [1]. This radiation arises owing to the excitation of alternate high-frequency displacement and conduction currents in an object subjected to testing between the flexible plates of a capacitive working sensor. The results from measurements (the obtained spectra) are analyzed using a hardware–software complex. For the research of aqueous solutions it is important to establish how the structure of water is influenced by temperature [2]. In Fig. 1 shows the changes in the spectra of water temperature. The spectral pattern changes when the water is frozen to ice (spectra 2). Additional peaks emerge in the right side of the spectrum, beginning at a frequency of 2456.54MHz. After the water returns to the liquid state (spectra 3) at the reference temperature (25°C), the spectra differ from the initial one by shifting toward an increase in the frequency of the spectra and a drop in the amplitudes of all peaks. Finally we have to say that:

1. The method of radioscopy in the microwave range, allows you to explore the fluid system, by comparing the spectra of the pure solvent (reference samples) and solutions.

2. In this work, the parameters of the spectra of the standard with bidistilled water and aqueous solutions: individual substances in the analyzed water; the difference of the concentrations of dissolved substances; evaluation of isotopic composition in the system of hydrogen isotopes.

3. It was established experimentally that this method can detect the presence of small quantities of heavy (D) and superheavy (T) hydrogen isotopes in ordinary (H2O) and heavy (D2O) water

Fig. 1 Spectra of water in different states: (1) initial state at 299 K, (2) frozen state at 273 K, (3) thawed state at 299 K.

Speaker
Biography:

Pujarini Banerjee has expertise in the technique of matrix isolation spectroscopy, and her research interests involve the infrared spectroscopic probing of binary hydrogen bonded complexes. The objective is to decipher the nature of intermolecular interactions that best describe the spectral shifts of the groups involved in non-covalent binding.  The complexes studied are mostly of biological or atmospheric interest, and include both conventional and non-conventional variants of hydrogen bonds. The observed spectral shifts are interpreted in terms of various structural and energetic parameters predicted by electronic structure theory. Pujarini got her doctoral degree from the University of Calcutta, and is currently working as a post-doctoral researcher under the supervision of Prof. Tapas Chakraborty, at the Department of Physical Chemistry, Indian Association for the Cultivation of Science, Kolkata, India.

Abstract:

Matrix isolation infrared spectroscopic studies of two binary O-H···π hydrogen bonded complexes of formic acid (FA) and phenol (Ph) with benzene (Bz), and a series of binary O-H···O hydrogen bonded fluorophenol-water complexes will be reported. In the first category, complexation results in red shifts of O-H stretching fundamentals (νOH) of Ph and FA by ~78 and ~120 cm-1, respectively,1,2 and the latter is the largest shift known so far for a binary complex of an O-H donor with π-orbitals of Bz as acceptor. We propose to use these observed red-shifts as benchmarks to test the accuracy of electronic structure methods in predicting geometries of the two complexes. We have noted that popularly used electronic structure theory methods with larger sized basis sets do not always predict structures that are consistent with the observed νOH shifts. This holds especially for the complex of Bz with FA, which will be discussed in detail.2,4,5 In the case of binary fluorophenol-water complexes, we have observed systematic νOH red-shifts of the fluorophenol-donors, which increase by ~90 % from phenol to pentafluorophenol.3 Surprisingly, the magnitudes of the spectral shifts of the binary complexes display excellent linear correlation with the aqueous phase pKa values of the fluorophenols. Furthermore, the shifts display poor correlation with the total binding energies of the complexes, as signatures of deviation from the well-known Badger-Bauer rules. On the other hand, it has been shown that the spectral shifts relate nicely with the local quantum-chemical charge transfer (CT) interactions at the site of hydrogen bonding. We infer that this local interaction is the primary determining factor for spectral red-shifts of the donor in such binary complexes, and the same also holds for O-H···π hydrogen bonded dimers.

Speaker
Biography:

I was born in 1963. In 1986 I graduated from “Electronic equipment” faculty of Moscow Power Engineering Institute. In 1986-2006 I worked, as scientific officer, at “Physics and technique of high voltage” laboratory in Physics Institute of Azerbaijan National Academy of Sciences and in 1995 was received the scientific degree of PhD in Physics. In 2006-2010 I studied, as a doctorate at "Technique and electro physics of high voltage" chair in Moscow Power Engineering Institute. Now I work, as a chief engineer, at "Scientific researches and international relations" department of “Azersu” OJSC. My scientific research is related to development of power effective and environmentally clear high-voltage installations, elaboration of green electro technologies for treatment and cleaning of toxic emissions of chemical, metallurgical and other harmful productions, various fluid food products for extension their storage terms, drinking water and waste water from organic and inorganic contaminants and pathogenic microorganisms.

Abstract:

In presented article the high-voltage technology for inactivation of drinking water and wasterwater from various microbes and viruses is considered. As a power source and investigated object – high voltage pulsed generator with output tension 100 kV and water mediums (drinking and waste water) with contained microorganisms respectively were used [1, 2].  At influence of high electric fields in water both thermal and electric processes with formation of gas inclusions and plasma channels respectively, generation of high-frequency radiation (infrared, visible, ultraviolet and X-ray) are taken place. Results of experiments and calculations confirm dependence of usefull emitted energy in water from some parameters of electrode system (radius of curvature, bared area of “pin” electrode and inter-electrode distance). In addition, electric processes in water are also depended from medium’s electro conductivity. At tensions less 20 kV only thermal and electrolysis processes in water are taken place. Above 20 kV ionization processes in gas inclusions with formation of conductive leader channels by high temperature and pressure, moving to opposite electrode at subsonic and supersonic speeds are occured. It is depending from voltage amplitude and polarity. Discharge processes are accompanied by shock ionization, photoionization, and in combination of micro and nanopulse effects by formation of high-energy electron beams that cause X-rays. As a result of dissociation of water molecules and atoms under effect of strong electropulsed fields is occurred accumulation of metal ions on membrane, which play the bridge role for penetration of electric fields into cell [3-5]. It can cause explosive processes within the membrane and cause its destruction. With shortening the pulse front is improving penetration of high-frequency pulsed fields directly into the nucleus of biological cell. Microbiological analyses of treated water were shown, that concentrations of available bacteria and viruses are below the maximum allowable.