'Divide-and-conquer' semiclassical molecular dynamics: An application to water clusters

TL;DR

This paper introduces a divide-and-conquer semiclassical method to simulate vibrational spectra of water clusters up to decamers, effectively capturing quantum effects in high-dimensional systems with results aligning well with prior estimates.

Contribution

The study develops and applies a novel divide-and-conquer semiclassical approach for high-dimensional water clusters, enabling accurate vibrational spectra simulations.

Findings

Good agreement with previous variational estimates for bending and high-frequency modes

Red shifts observed in hydrogen-bond influenced modes, sometimes substantial

Method successfully applied to systems with up to 84 vibrational degrees of freedom

Abstract

We present an investigation of vibrational features in water clusters performed by means of our recently established divide-and-conquer semiclassical approach [M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 119, 010401 (2017)]. This technique allows us to simulate quantum vibrational spectra of high-dimensional systems starting from full-dimensional classical trajectories and projection of the semiclassical propagator onto a set of lower dimensional subspaces. The potential energy surface employed is a many-body representation up to three-body terms, in which monomers and two-body interactions are described by the high level Wang-Huang-Braams-Bowman (WHBB) water potential, while, for three-body interactions, calculations adopt a fast permutationally invariant ab initio surface at the same level of theory of the WHBB 3-body potential. Applications range from the water dimer up to the water decamer, a system made of 84 vibrational degrees of freedom. Results are generally in agreement with previous variational estimates in the literature. This is particularly true for the bending and the high-frequency stretching motions, while estimates of modes strongly influenced by hydrogen bonding are red shifted, in a few instances even substantially, as a consequence of the dynamical and global picture provided by the semiclassical approach.