Toward a universal water model: First principles simulations from the dimer to the liquid phase

TL;DR

This paper introduces HBB2-pol, a first-principles water model that accurately simulates water from small clusters to the liquid phase, matching experimental data and quantum calculations, enabling detailed molecular-level understanding.

Contribution

The paper presents HBB2-pol, a novel first-principles water model that accurately predicts properties across different phases and cluster sizes, advancing molecular simulations of water.

Findings

HBB2-pol reproduces virial coefficients and vibrational spectra accurately.

The model predicts energy differences between water cluster isomers within high-level electronic structure accuracy.

Simulations with HBB2-pol match structural and dynamical properties of liquid water.

Abstract

A full-dimensional molecular model of water, HBB2-pol, derived entirely from first principles, is introduced and employed in computer simulations ranging from the dimer to the liquid. HBB2-pol provides excellent agreement with the measured second and third virial coefficients and, by construction, reproduces the dimer vibration-rotation tunneling spectrum. The model also predicts the relative energy differences between isomers of small water clusters within the accuracy of highly correlated electronic structure methods. Importantly, when combined with simulation methods that explicitly include zero-point energy and quantum thermal motion, HBB2-pol accurately describes both structural and dynamical properties of the liquid phase. The predictive power of the HBB2-pol quantum simulations opens the door to the long-sought molecular-level understanding of water under different conditions and in different environments.