研究领域

Computational/Theoretical Chemistry Materials Chemistry Physical Chemistry Ultrafast Dynamics

Modern computational chemistry strives to provide an atomistically detailed dynamical description of fundamental chemical processes. The strategy for reaching this goal generally follows a two-step program. In the first step, electronic structure calculations are used to obtain the force fields that the nuclei are subject to. In the second step, molecular dynamics simulations are used to describe the motion of the nuclei. The first step is always based on quantum mechanics, in light of the pronounced quantum nature of the electrons. However, the second step is most often based on classical mechanics. Indeed, classical molecular dynamics simulations are routinely used nowadays for describing the dynamics of complex chemical systems that involve tens of thousands of atoms. However, there are many important situations where classical mechanics cannot be used for describing the dynamics. Our research targets the most chemically relevant examples include: (1) Linear and nonlinear vibrational and electronic spectroscopy. The transition frequencies in these cases are often much larger than kT. Furthermore, in the spectral signals can be expressed in terms of optical response functions that lack a well defined classical limit. (2) Vibrational and electronic relaxation. The quantum nature of the pathways of irradiative intramolecular energy redistribution within molecules and intermolecular energy transfer between molecules is attributed to the large gap between vibrational and electronic energy levels. (3) Proton and electron transfer reactions. The elementary steps of many complex chemical processes are based on such reactions. Their pronounced quantum nature is attributed to the light mass of protons and electrons, which often gives rise to quantum tunneling and zero-point energy effects. The challenge involved in simulating the quantum molecular dynamics of such systems has to do with the fact that the computational effort involved in solving the time-dependent Schrödinger equation is exponentially larger than that involved in solving Newton’s equations. As a result, a numerically exact solution of the Schrödinger equation is not feasible for a system that consists of more than a few atoms. The main research thrust of the Geva group is aimed at developing rigorous and accurate mixed quantum-classical, quasi-classical and semiclassical methods that would make it possible to simulate equilibrium and nonequilibrium quantum dynamics of systems that consist of hundreds of atoms and molecules. We put emphasis on applications to experimentally-relevant disordered complex condensed phase systems such as molecular liquids, which serve as hosts for many important chemical processes. We also specialize in modeling and analyzing different types of time resolved electronic and vibrational spectra that are used to probe molecular dynamics in those systems, often in collaboration with experimental groups.

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Wilcox, D.; Lee, M.; Sykes, M.; Niedringhaus, A.; Geva, E.; Dunietz, B.; Shtein, M.; Ogilvie, J. Ultrafast Charge-Transfer Dynamics at the Boron Subphthalocyanine Chloride/C60 Heterojunction: Comparison between Experiment and Theory. J. Phys. Chem. Lett. 2015, 6, 569–575. Talapatra S.; Geva E. Vibrational Lifetimes of Cyanide Ion in Aqueous Solution from Molecular Dynamics Simulations: Intermolecular vs Intramolecular Accepting Modes. J. Phys. Chem. B 2014, 118, 7395–7404. Lee, M.; Geva, E.; Dunietz, B. Donor-to-Donor vs. Donor-to-Acceptor Interfacial Charge Transfer States in the Phthalocyanine-Fullerene Organic Photovoltaic System. J. Phys. Chem. Lett. 2014, 5, 3810-3816. Talapatra, S.; Geva E. Vibrational Lifetimes of Cyanide Ion in Aqueous Solution From Molecular Dynamics Simulations: Intermolecular vs. Intramolecular Accepting Modes. J. Phys. Chem. B 2014, 118, 7395-7404. Zheng, Z.; Manna, A.; Hendrickson, H. P.; Hammer, M.; Song, C.; Geva, E.; Dunietz, B. Molecular Structure, Spectroscopy and Photo-Induced Kinetics in Tri-Nuclear Cyanide Bridged Complex in Solution: A First Principle Perspective. J. Am. Chem. Soc. 2014, 136, 16954–16957. Lee, M.; Geva, E.; Dunietz, B. Calculation from First Principles of Golden-Rule Rate Constants for Photo-Induce Subphthalocyanine/Fullerene Interfacial Charge Transfer and Recombination in Organic Photovoltaic Cells. J. Phys. Chem. C 2014, 118, 9780-9789. Vazquez, F. X.; Talapatra, S.; Sension, R. J.; Geva, E. The Entropic Origin of Solvent Effects on the Single Bond cZt-tZt Isomerization Rate Constant of 1,3,5-cis-Hexatriene in Alkane and Alcohol Solvents: A Molecular Dynamics Study. J. Phys. Chem. B 2014, 118, 7395-7404. Phillips, H. D.; Zheng, Z.; Geva, E.; Dunietz, B. D. Orbital Gap Predictions for Rational Design of Organic Photovoltaic Materials. Organic Electronics 2014, 15, 1509-1520. Kwac, K.; Geva, E. A Mixed Quantum-Classical Molecular Dynamics Study of anti-Tetrol and syn-Tetrol Dissolved in Liquid Chloroform II: Infrared Emission Spectra, Vibrational Excited-State Lifetimes, and Nonequilibrium Hydrogen-Bond Dynamics. J. Phys. Chem. B 2013, 117, 14457-14467. Kwac, K.; Geva, E. A Mixed Quantum-Classical Molecular Dynamics Study of anti-Tetrol and syn-Tetrol Dissolved in Liquid Chloroform: Hydrogen-Bond Structure and Its Signature on the Infrared Absorption Spectrum. J. Phys. Chem. B 2013, 117, 16493-16505. Lee, M.; Dunietz, B. D.; Geva, E. Calculation from First Principles of Intramolecular Golden-Rule Rate Constants for Photo-Induced Electron Transfer in Molecular Donor-Acceptor Systems. J. Phys. Chem. C 2013, 117, 23391-23401. Kwac, K.; Geva, E. Solvation Dynamics of Formylperylene Dissolved in Methanol-Acetonitrile Liquid Mixtures: A Molecular Dynamics Study. J. Phys. Chem. B 2013, 117, 9996-10006. Kwac, K.; Geva E. A Mixed Quantum-Classical Molecular Dynamics Study of the Hydroxyl Stretch in Methanol/Carbon-Tetrachloride Mixtures III: Nonequilibrium Hydrogen-Bond Dynamics and Infrared Pump-Probe Spectra. J. Phys. Chem. B 2013, 117, 7737-7749. Zheng, S.; Geva, E.; Dunietz, B. D. Solvated Charge Transfer States of Functionalized Anthracene and Tetracyanoethylene Dimers: A Computational Study Based on a Range Separated Hybrid Functional and Charge Constrained Self-Consistent Field with Switching Gaussian Polarized Continuum Models. J. Chem. Theory Comput. 2013, 9, 1125-1131. Phillips, H.; Geva, E.; Dunietz, B. D. Calculating Off-Site Excitations in Symmetric Donor–Acceptor Systems via Time-Dependent Density Functional Theory with Range-Separated Density Functionals. J. Chem. Theory Comput. 2012, 8, 2661-2668. Zheng, S.; Phillips, H.; Geva, E.; Dunietz, B. D. Ab Initio Study of the Emissive Charge-Transfer States of Solvated Chromophore-Functionalized Silsesquioxanes. J. Am. Chem. Soc. 2012, 134, 6944–6947. Kwac, K.; Geva, E. Mixed Quantum-Classical Molecular Dynamics Study of the Hydroxyl Stretch in Methanol/Carbon-Tetrachloride Mixtures II: Excited State Hydrogen Bonding Structure and Dynamics, Infrared Emission Spectrum, and Excited State Lifetime. J. Phys. Chem. B 2012, 116, 2856–2866. Phillips, H.; Zhang, S.; Hyla, A.; Laine, R.; Goodson, T.; Geva, E.; Dunietz, B. D. Ab Initio Calculation of the Electronic Absorption of Functionalized Octahedral Silsesquioxanes via Time-Dependent Density Functional Theory with Range-Separated Hybrid Functionals. J. Phys. Chem. A 2011, 116, 1137–1145. Kwac, K.; Geva, E. A Mixed Quantum-Classical Molecular Dynamics Study of the Hydroxyl Stretch in Methanol/Carbon Tetrachloride Mixtures: Equilibrium Hydrogen-Bond Structure and Dynamics at the Ground State and the Infrared Absorption Spectrum. J. Phys. Chem. B 2011, 115, 9184–9194. Vazquez, F. X.; Talapatra, S.; Geva, E. Vibrational Energy Relaxation in Liquid HCl and DCl via the Linearized Semiclassical Method: Electrostriction versus Quantum Delocalization. J. Phys. Chem. A 2011, 115, 9775–9781.