A tight binding model for water

TL;DR

This paper introduces a novel tight binding model for water that accurately predicts structural and electronic properties, including the increase in molecular dipole moments from clusters to bulk, aligning well with experimental data.

Contribution

A new tight binding model for water that is fitted using only monomer and dimer data, capable of predicting properties of larger clusters, ice, and liquid water.

Findings

Reproduces the two-fold increase in molecular dipole moments in clusters.

Accurately models properties of liquid water consistent with experiments.

Provides insights into density differences between water and ice.

Abstract

We demonstrate for the first time a tight binding model for water incorporating polarizable anions. A novel aspect is that we adopt a "ground up" approach in that properties of the monomer and dimer only are fitted. Subsequently we make predictions of the structure and properties of hexamer clusters, ice-XI and liquid water. A particular feature, missing in current tight binding and semiempirical hamiltonians, is that we reproduce the almost two-fold increase in molecular dipole moment as clusters are built up towards the limit of bulk liquid. We concentrate on properties of liquid water which are very well rendered in comparison with experiment and published density functional calculations. Finally we comment on the question of the contrasting densities of water and ice which is central to an understanding of the subtleties of the hydrogen bond.