Local structural effects on intermolecular vibrations in liquid water: The instantaneous-normal-mode analysis

Abstract

Currently, the designations for the low-frequency vibrational spectrum of liquid watrer are still diversified. In this paper, the water molecules simulated by the SPC/E model are classified into subensembles, characterized by their local structures, which are specified in two different ways: the geometry of Voronoi polyhedron or the H-bond configuration. Using the instantaneous normal mode (INM) analysis for these subensembles, we investigate the effects of local structure on the low-frequency INM spectrum of liquid water. From the contributions of these subensembles to the translational INM spectrum, our results provide insights into the geometric effects of local structure and the H-bond configuration on intermolecular vibrations in liquid water.