Hydrogen bonded configurations in liquid water and their correlations with local tetrahedral structures

Abstract

Hydrogen-bonded structures in liquid water lies at the root of its many anomalous properties. The ability of water to form hydrogen bonds is perceived to be the reason for the formation of locally favored tetrahedral structures (LFTS) in liquid water. These tetrahedral environments also lay the foundation for the two-state theories of water. In molecular dynamics simulations, hydrogen bonds are often assigned between molecules if they satisfy certain geometric or energetic criteria, or a combination of both. Potential of Mean Force landscapes may be used to identify the geometric criteria for identifying hydrogen bonds, and distinguishing ‘ice-like’ hydrogen bonds. In this work, we report the statistical information of hydrogen-bonded structures in liquid water from molecular simulations of the iAMOEBA water model. The fraction of different hydrogen-bonded structures is also compared with the fraction of LFTS molecules to gain insights into the hydrogen-bonded configuration of LFTS molecules. The structure of different hydrogen-bonded configurations, using various structural descriptors is also reported. We find that tetrahedral environments in liquid water (as modeled by the iAMOEBA force-field) are largely, but not exclusively constituted by the molecules that donate and accept two hydrogens each when ‘ice-like’ hydrogen bonds are considered.