Kirill A. Velizhanin

Dynamics of electron transfer reactions in the presence of mode mixing: comparison of a generalized master equation approach with the numerically exact simulation.

A generalized master equation approach is developed to describe electron transfer (ET) dynamics in the presence of mode mixing. Results from this approximate approach are compared to the numerically exact simulations using the multilayer multiconfiguration time-dependent Hartree theory. The generalized master equation approach is found to work well for nonadiabatic resonant ET. Depending on the specific situation, it is found that the introduction of mode mixing may either increase or decrease the ET time scale. The master equation fails in the adiabatic ET regime, where the introduction of mode mixing may lead to electron trapping. From both the approximate theory and the numerically exact simulation it is shown how neglecting mode mixing in practical calculations may lead to inaccurate predictions of the ET dynamics.

Meir–Wingreen formula for heat transport in a spin-boson nanojunction model

An analog of the Meir-Wingreen formula for the steady-state heat current through a model molecular junction is derived. The expression relates the heat current to correlation functions of operators acting only on the degrees of freedom of the molecular junction. As a result, the macroscopic heat reservoirs are not treated explicitly. This allows one to exploit methods based on a reduced description of the dynamics of a relatively small part of the overall system to evaluate the heat current through a molecular junction. The derived expression is applied to calculate the steady-state heat current in the weak coupling limit, where the Redfield theory is used to describe the reduced dynamics of the molecular junction. The results are compared with those of previously developed approximate and numerically exact methods.

Topological quantization of energy transport in micromechanical and nanomechanical lattices | NIST

Chih-Chun Chien,1 Kirill A. Velizhanin,2 Yonatan Dubi,3 B. Robert Ilic,4 and Michael Zwolak4,* 1School of Natural Sciences, University of California, Merced, California 95343, USA 2Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 3Department of Chemistry and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel 4Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

Nonequilibrium solvent effects in Born-Oppenheimer molecular dynamics for ground and excited electronic states.

The effects of solvent on molecular processes such as excited state relaxation and photochemical reaction often occurs in a nonequilibrium regime. Dynamic processes such as these can be simulated using excited statemolecular dynamics. In this work, we describe methods of simulating nonequilibrium solvent effects in excited statemolecular dynamics using linear-response time-dependent density functional theory and apparent surface charge methods. These developments include a propagation method for solvent degrees of freedom and analytical energy gradients for the calculation of forces. Molecular dynamics of acetaldehyde in water or acetonitrile are demonstrated where the solute-solvent system is out of equilibrium due to photoexcitation and emission.