Generalized discrete truncated Wigner approximation for nonadiabatic quantum-classical dynamics

Year: 2021

Authors: Lang H., Vendrell O., Hauke P.

Autors Affiliation: Theoretical Chemistry, Institute of Physical Chemistry, Heidelberg University, Im Neuenheimer Feld 229, Heidelberg, 69120, Germany; INO-CNR BEC Center, Department of Physics, University of Trento, Via Sommarive 14, Trento, I-38123,Italy; Department of Physics, University of Trento, Via Sommarive 14, I-38123 Trento, Italy

Abstract: Nonadiabatic molecular dynamics occur in a wide range of chemical reactions and femtochemistry experiments involving electronically excited states. These dynamics are hard to treat numerically as the system?s complexity increases, and it is thus desirable to have accurate yet affordable methods for their simulation. Here, we introduce a linearized semiclassical method, the generalized discrete truncated Wigner approximation (GDTWA), which is well-established in the context of quantum spin lattice systems, into the arena of chemical nonadiabatic systems. In contrast to traditional continuous mapping approaches, e.g., the Meyer-Miller-Stock-Thoss and the spin mappings, GDTWA samples the electron degrees of freedom in a discrete phase space and thus forbids an unphysical unbounded growth of electronic state populations. The discrete sampling also accounts for an effective reduced but non-vanishing zero-point energy without an explicit parameter, which makes it possible to treat the identity operator and other operators on an equal footing. As numerical benchmarks on two linear vibronic coupling models and Tully?s models show, GDTWA has a satisfactory accuracy in a wide parameter regime, independent of whether the dynamics is dominated by relaxation or by coherent interactions. Our results suggest that the method can be very adequate to treat challenging nonadiabatic dynamics problems in chemistry and related fields.


Volume: 155 (2)      Pages from: 024111-1  to: 024111-11

More Information: We acknowledge support from Provincia Autonoma di Trento, the ERC Starting Grant StrEnQTh (Project No. 804305), and Q@TN-Quantum Science and Technology in Trento. H.L. thanks Hans-Dieter Meyer and Markus Schroder for assistance with the MCTDH simulations.
KeyWords: zero-point energy; molecular-dynamics; phase-space; semiclassical description; electronic degrees
DOI: 10.1063/5.0054696