The Beran Group at UC Riverside
Michael G. Mavros , Troy Van Voorhis.
Coulomb explosion during the early stages of the reaction of alkali metals with water. Philip E.
Entropies of Condensed Phases and Complex Systems
Development of highly accurate approximate scheme for computing the charge transfer integral. Energy decomposition analysis approaches and their evaluation on prototypical protein-drug interaction patterns. Tautermann , Chris-Kriton Skylaris.
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Quantum chemical approach for condensed-phase thermochemistry (III)
The Journal of Chemical Physics [01 Oct , 14 ]. Abstract The recently proposed multilayer multiconfiguration time-dependent Hartree ML-MCTDH approach to evaluating reactive quantum dynamics is applied to two model condensed-phase proton transfer reactions. The models consist of a one-dimensional double-well "system" that is bilinearly coupled to a "bath" of harmonic oscillators parameterized to represent a condensed-phase environment. Numerically exact quantum-mechanical flux correlation functions and thermal rate constants are obtained for a broad range of temperatures and system-bath coupling strengths, thus demonstrating the efficacy of the ML-MCTDH approach.
Particular attention is focused on the regime where low temperatures are combined with weak system-bath coupling. Under such conditions it is found that long propagation times are often required and that quantum coherence effects may prevent a rigorous determination of the rate constant.
Nonetheless, accurate treatment of inter-particle interactions, in terms of quantum chemical first principles methods, is a prerequisite for many applications, because of the complexity of both reactants and solvents in modern molecular sciences. Currently, a straightforward calculation of thermodynamic properties from these methods is only possible for high-temperature and low- density systems.
Although the enthalpy of a system can often be predicted to a good level of precision with this ideal gas approach, calculating the entropy contribution to the free energy is problematic, especially as the density of the system increases. This thesis contains a compact and coherent introduction of basic theoretical features. The foundations are then laid for the development of approaches suitable for calculation of condensed phase entropies on the basis of well-established quantum chemical methods. The main emphasis of this work is on realistic systems in solution, which is the most important environment for chemical synthesis.
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