A Quantum-Classical Liouville Formalism in a Preconditioned Basis and Its Connection with Phase-Space Surface Hopping

TL;DR

This paper establishes a connection between a phase-space surface hopping method and a quantum-classical Liouville equation, demonstrating improved modeling of nonadiabatic dynamics with complex Hamiltonians and capturing geometric magnetic effects.

Contribution

It shows that a pseudo-diabatic phase-space surface hopping approach is consistent with a preconditioned quantum-classical Liouville equation, offering new insights and improvements over standard methods.

Findings

PD-PSSH captures geometric magnetic effects

Preconditioned QCLE can outperform standard QCLE

Constructs a mean-field Ehrenfest algorithm in phase space

Abstract

We revisit a recent proposal to model nonadiabatic problems with a complex-valued Hamiltonian through a phase-space surface hopping (PSSH) algorithm employing a pseudo-diabatic basis. Here, we show that such a pseudo-diabatic PSSH (PD-PSSH) ansatz is consistent with a quantum-classical Liouville equation (QCLE) that can be derived following a preconditioning process, and we demonstrate that a proper PD-PSSH algorithm is able to capture some geometric magnetic effects (whereas the standard FSSH approach cannot). We also find that a preconditioned QCLE can outperform the standard QCLE in certain cases, highlighting the fact that there is no unique QCLE. Lastly, we also point out that one can construct a mean-field Ehrenfest algorithm using a phase-space representation similar to what is done for PSSH. These findings would appear extremely helpful as far understanding and simulating nonadiabatic dynamics with complex-valued Hamiltonians and/or spin degeneracy.