Day 1 :
University of Heidelberg, Germany
Time : 09:30-10:05
Horst Köppel has been a Senior Lecturer, and later Professor of Theoretical Chemistry at Heidelberg University since 1991. His research interests focuses on the theory of the Jahn-Teller effect, molecular excited state processes and vibrational structure in electronic spectra; special focus is on phenomena which cannot be described within the conventional Born-Oppenheimer separation of electronic and nuclear motions. He has authored and coauthored about 250 peer-reviewed original research papers, edited three books with topical reviews and organized several conferences in the field.
The author will present an overview over the theoretical work on molecular dynamics following photoexcitation in the visible or UV spectral range. This carries the system to an electronically excited state with a potential energy surface (PES) differing from that of the electronic ground state. A rich variety of vibrational and related processes will thus be initiated which can proceed on a single or several of the many different excited-state PESs. If some of these PESs are close in energy they interact and the nuclear motion on them does not proceed independently. This is the realm of nonadiabatic molecular dynamics which has been in the focus of interest of spectroscopists and physical and theoretical chemists for many years. It is of fundamental importance for many different excited-state processes in biology, chemistry and physics (such as charge transfer, photochemical rearrangements etc.). A typical scenario are so-called conical intersections of potential energy surfaces where different PES become degenerate upon variation of two nuclear coordinates. Systems treated by us recently comprise SO2, small polyenes like butadiene or hexatriene or the benzene cation. Key features of the systems and methods used will be highlighted in the talk.
Schematic repres-entation of two conical inter-sections and their associated photochemical reaction pathways.
Institute of Organic Chemistry and Biochemistry – CAS, Czech Republic
Time : 10:05-10:40
Pavel Hobza (dr.hc, FRSC) obtained his PhD (1974) from the Institute of Physical Chemistry of the Academy of Science of the Czech Republic. He is a Distinguished Chair at the Institute of Organic Chemistry and Biochemistry of the Academy of Sciences of the Czech Republic, Prague, Czech Republic. His research team works on noncovalent interactions and their applications in bio- and material sciences, databases of accurate interaction energies and on in silico drug design. He has co-authored 4 books, more than 450 papers and 35 review papers in peer-reviewed journals, his H-index (WOS) is 98, sum of Times Cited is more than 35,000. He was awarded by “Highly Cited Researcher” in chemistry during 2014-2016 (Thomson Reuters, later Clarivate Analytics) and Schrödinger Medal in 2017 (World Association of Theoretical and Computational Chemists).
Noncovalent interactions play an important role in chemistry, physics and biology. Reliable characteristics like stabilization energy, structure and vibrational frequencies are obtained using composite coupled cluster schemes which offer the possibility of improving the accuracy of results obtained by adding excitation operators of increasing order. It was shown that already CCSD(T)/ CBS method yields an accurate and reliable description of noncovalent interactions, yet is only applicable to systems with several tens of atoms. Lower-level methods like DFT or semiempieical QM (SQM) should be parametriezed or verified and here the databases of accurate stabilization energies and geometries developed in our laboratory (S22, S66, X40 and L7) play an indispensable role. Binding free energy for host-guest and protein-ligand complexes is constructed as a sum of gas-phase interaction energy (ΔEint), change of desolvation free-energy (ΔΔGsolv), change of the conformational free energy of both components (ΔGconfw) and entropy term (eq. 1): ΔGw ≈ ΔEint + ΔΔGsolv + ΔGconfw – TΔS (1). Because of the size of systems investigated the DFT-D, and PM6 or SCC-DF-TB SQM methods combined with COSMO technique were considered. Performance of these methods was verified by comparison of interaction energies of model complexes with the benchmark values obtained from CCSD(T) and MP2.5 methods. Applicability of procedures described is demonstrated for evaluation of binding free energies of several extended systems like host – guest, protein – ligand and surface – admolecule ones.