Quantum dynamical effects in liquid water: A semiclassical study on the diffusion and the infrared absorption spectrum

Abstract

The important role of liquid water in many areas of science from chemistry, physics, biology, geology to climate research, etc., has motivated numerous theoretical studies of its structure and dynamics. The significance of quantum effects on the properties of water, however, has not yet been fully resolved. In this paper we focus on quantum dynamical effects in liquid water based on the linearized semiclassical initial value representation (LSC-IVR) with a quantum version of the simple point charge/flexible (q-SPC/fw) model [Paesani et al., J. Chem. Phys. 125, 184507 (2006)] for the potential energy function. The infrared (IR) absorption spectrum and the translational diffusion constants have been obtained from the corresponding thermal correlation functions, and the effects of intermolecular and intramolecular correlations have been studied. The LSC-IVR simulation results are compared with those predicted by the centroid molecular dynamics (CMD) approach. Although the LSC-IVR and CMD results agree well for the broadband for hindered motions in liquid water, the intramolecular bending and O-H stretching peaks predicted by the LSC-IVR are blueshifted from those given by CMD; reasons for this are discussed. We also suggest that the broadband in the IR spectrum corresponding to restricted translation and libration gives more information than the diffusion constant on the nature of quantum effects on translational and rotational motions and should thus receive more attention in this regard.

Zero-point energy constrained quasiclassical, classical, and exact quantum simulations of isomerizations and radial distribution functions of the water trimer using an ab initio potential energy surface

“…Therefore, in applications in the condensed phase ZPE is ignored and instead a purely classical phase space sampling is done. However, several applications have demonstrated the importance of ZPE in MD calculations, thus the absence of the ZPE in the standard classical MD is a significant issue [6][7][8][9][10]. Indeed, in gasphase reaction dynamics calculations the quasiclassical trajectory (QCT) method is frequently used, in which the reactants have ZPE.…”

Boltzmann-conserving classical dynamics in quantum time-correlation functions: “Matsubara dynamics”

“…But there are plenty of cases, e.g. the spectrum of liquid water, [3][4][5] hydrogen-diffusion on metals, 6,7 and proton/hydride-transfer reactions, [8][9][10][11][12][13] for which one needs to evaluate time-correlation functions of the form 1 Z C AB (t) = 1…”

“…für Physikalische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland b) Corresponding author: sca10@cam.ac.uk approximation), 3,[15][16][17][18][19][20][21][22][23][24][25][26][27] in which the quantum Liouvillian is expanded as a power series in 2 , then truncated at 0 . Miller 15,16 and later Shi and Geva 17 showed that this approximation is equivalent to linearizing the displacement between forward and backward Feynman paths in the exact quantum time-propagation, which removes the coherences, thus making the dynamics classical.…”

Exact quantum statistics for electronically nonadiabatic systems using continuous path variables

“…41,[68][69][70] The PI-ST representation of the Boltzmann operator can be substituted in the expression for the TCF in Eq. (40) to obtain…”