The quantum trajectory‐guided adaptive Gaussian methodology in the Libra software package

Abstract

In this paper, we report an implementation of the quantum trajectory‐guided adaptive Gaussian (QTAG) method in a modular open‐source Libra package for quantum dynamics calculations. The QTAG method is based on a representation of wavefunctions in terms of a quantum trajectory‐guided adaptable Gaussians basis and is generalized for time‐propagation on multiple coupled surfaces to be applicable to model nonadiabatic dynamics. The potential matrix elements are evaluated within either the local harmonic or bra‐ket‐average (linear) approximations to the potential energy surfaces, the latter being a more practical option. Performance of the QTAG method is demonstrated and discussed for the Holstein and Tully models, which are the standard benchmarks for method development in the area of nonadiabatic dynamics.

Nonadiabatic Dynamics with Exact Factorization: Implementation and Assessment

“…Even though the original CTMQC method cannot capture the coherence originating from the accidental wave packet overlap, an alternative CTMQC framework that could present a new coherence descriptor and fix the coherence problem may still be possible to develop in future. Also, utilizing quantum trajectories based on Bohmian mechanics would be another candidate. ,, After the first NA transition, the classical trajectories are separated, propagating on each adiabatic PES. These branched trajectory-based wave packets behave independently toward the end of the dynamics.…”

“…To fill in the identified gap, we first implement the XF-based ITMQC methods in the Libra package, , which is already equipped with the range of traditional trajectory surface hopping (TSH) methods for NA dynamics methods as well as with fully quantum dynamics (QD) algorithms and can be used both with model Hamiltonians − and with atomistic systems. − We present a self-contained account on the theoretical grounds of the methods implemented, as well as the corresponding algorithmic details. We pay special attention to seemingly simple but practically nasty topics of state tracking and phase correction.…”

Generalization of the Local Diabatization Approach for Propagating Electronic Degrees of Freedom in Nonadiabatic Dynamics

“…In the present work, we approach the problem of the phase consistency correction and state identity tracking from the conceptually satisfying viewpoint of basis re-expansion. This re-expansion approach is also motivated by the recently presented integrator for the quantum trajectory with adaptive Gaussians (QTAG) methodology [40] as well as by the TD-SE integration in a quasi-diabatic basis. [41] Although we rely on the well-known ideas, we use them to develop a unified and self-consistent formalism for state tracking and phase correction.…”