A second order thermodynamic perturbation theory for hydrogen bond cooperativity in water

TL;DR

This paper develops a second order thermodynamic perturbation theory to accurately model hydrogen bond cooperativity in water, improving predictions of water's structure over traditional pairwise models.

Contribution

It introduces a second order correction to association theory to account for hydrogen bond cooperativity in water, enhancing the accuracy of structural predictions.

Findings

The theory predicts water's hydrogen bonding structure as a function of temperature and density.

It shows substantial differences from first order models that neglect cooperativity.

Predictions align well with spectroscopy, neutron diffraction, and molecular simulation data.

Abstract

It has been extensively demonstrated through first principles quantum mechanics calculations that water exhibits strong hydrogen bond cooperativity. Classical molecular simulation and statistical mechanics methods typically assume pairwise additivity, meaning they cannot account for these 3-body and higher cooperative effects. In this document, we extend second order thermodynamic perturbation theory to correct for hydrogen bond cooperativity in 4 site water. We show that the association theory gives substantially different predictions than the first order result, which does not include hydrogen bond cooperativity. By comparison to spectroscopy, neutron diffraction and molecular simulation data, we show that the theory accurately predicts the hydrogen bonding structure of water as a function of temperature and density.