On the representation of many-body interactions in water

TL;DR

This paper investigates how different approaches to modeling many-body interactions affect the accuracy of water potential energy surfaces and dipole moment surfaces, emphasizing the importance of explicit short-range terms for realistic simulations.

Contribution

It demonstrates that explicit short-range 2- and 3-body interactions are essential for accurate water models across phases and highlights the significance of a complete many-body dipole moment surface.

Findings

Explicit short-range interactions improve water potential accuracy.

Complete many-body dipole models are crucial for correct IR spectra.

Physically correct integration of interactions enhances model reliability.

Abstract

Recent work has shown that the many-body expansion of the interaction energy can effectively be used to develop analytical representations of global potential energy surfaces (PESs) for water. In this study, the role of short- and long-range contri- butions at different orders is investigated by analyzing water potentials that treat the leading terms of the many-body expansion through implicit (i.e., TTM3-F and TTM4-F PESs) and explicit (i.e., WHBB and MB-pol PESs) representations. It is found that explicit short-range representations of 2-body and 3-body interactions along with a physically correct integration of short- and long-range contributions are necessary for an accurate representation of the water interactions from the gas to the condensed phase. Similarly, a complete many-body representation of the dipole moment surface is found to be crucial to reproducing the correct intensities of the infrared spectrum of liquid water.