Approximate quantum trajectory dynamics for reactive processes in condensed phase

Abstract

A method of molecular dynamics with quantum corrections, practical for studies of large molecular systems, is reviewed. The approach is based on the Bohmian formulation of the time-dependent Schrödinger equation in which a wavefunction is represented by an ensemble of interdependent trajectories. The quantum effects come from the quantum potential acting on trajectories on par with the usual classical potential. The quantum potential is determined from the evolving nuclear wavefunction, i.e. from the quantum trajectory (QT) ensemble itself. For practical and conceptual reasons the quantum potential and corresponding quantum nuclear effect are computed only for the selected light nuclei. For studies of reactive chemical processes, the classical potential is computed on-the-fly using the density functional tight binding method of electronic structure. A massively parallel implementation, based on the message passing interface allows for efficient simulations of ensembles of thousands of trajectories describing systems of up to 200 atoms. As a biochemical application, the approximate QT approach is used to model the tunnelling-dominated proton transfer in soybean-lipoxygenase-1. A materials science application is represented by a study of the nuclear quantum effect on adsorption of hydrogen and deuterium on a C 37 H 15 molecule, which is a model 'flake' of graphene.Keywords: quantum effect; hybrid dynamics of quantum/classical nuclei; on-the-fly electronic structure; densityfunctional tight-binding method

The effect of local substrate motion on quantum hydrogen transfer in soybean lipoxygenase-1 modeled with QTES-DFTB dynamics

“…In the approximate quantum trajectory method [36], based on the de Broglie-Bohm representation of the time-dependent Schrödinger equation [37], a globally-defined quantum force acts on the trajectories in addition to the external potential (computed on-the-fly with DFTB). The substrate nuclei move according to a mixed quantum-classical framework, and their motion contributes to the wavefunction phase [38]. Delocalization of the donor carbon and acceptor oxygen wavefunctions was included by sampling their respective wavefunction in coordinate space.…”

Theoretical assessment of the nuclear quantum effects on polymer crystallinity via perturbation theory and dynamics

“…It is increasingly recognized that nuclear quantum effects (NQEs) associated with light nuclei, such as protons, may influence structure, dynamics and properties of large molecular systems and materials. The NQE studies are mainly focused on the zero‐point vibrational energy (ZPE), delocalization of the nuclear wavefunction and quantum tunneling . Liquid water is the prime example of a system in which NQEs are particularly important because of the central role of the hydrogen bonding on its properties .…”

“…The difference in stability of the hydrogen bonding and its deuterium‐substituted equivalent is due to the interplay of two competing quantum effects: the ZPE of vibrations and quantum tunneling. Some other systems, which may be influenced by the quantum behavior of the nuclei, are two‐dimensional materials and conducting polymers . Recent experiments have shown that selective deuteration of conducting polymers may change their optoelectronic properties .…”

Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules

“…(36), (37) and (41) are exact solutions of the TDSE that can connect full quantum dynamics to Ehrenfest dynamics. In this context these equations have been presented in a recent feature article [44].…”

“…The matching pursuit of Wu and Batista [35] and basis expansion leaping of Koch and Frankcombe [36] lie between clMCG and gMCG, using a time-independent basis that is periodically moved to expand the evolving wavepacket. The GBFs of the vMCG method itself move along non-classical trajectories, reminiscent of the quantum trajectories of Bohmian mechanics exemplified by the work of Garaschuk [37] and Curchod and Tavernelli [38].…”