On the efficient and accurate short-ranged simulations of uniform polar molecular liquids

TL;DR

This paper demonstrates that spherical truncations of 1/r interactions in models for water and acetonitrile are highly accurate in bulk simulations, and explains this using Local Molecular Field theory which accounts for corrections in nonuniform environments.

Contribution

It provides a theoretical framework based on LMF theory to explain the accuracy of spherical truncations in uniform molecular liquids and derives related equations for site-site models.

Findings

Spherical truncations yield accurate pair correlation functions in bulk liquids.

LMF theory explains the small corrections needed in uniform environments.

Derivations of YBG hierarchy and LMF theory are presented for molecular models.

Abstract

We show that spherical truncations of the 1/r interactions in models for water and acetonitrile yield very accurate results in bulk simulations for all site-site pair correlation functions as well as dipole-dipole correlation functions. This good performance in bulk simulations contrasts with the generally poor results found with the use of such truncations in nonuniform molecular systems. We argue that Local Molecular Field (LMF) theory provides a general theoretical framework that gives the necessary corrections to simple truncations in most nonuniform environments and explains the accuracy of spherical truncations in uniform environments by showing that these corrections are very small. LMF theory is derived from the exact Yvon-Born-Green (YBG) hierarchy by making physically-motivated and well-founded approximations. New and technically interesting derivations of both the YBG hierarchy and LMF theory for a variety of site-site molecular models are presented in appendices. The main paper focuses on understanding the accuracy of these spherical truncations in uniform systems both phenomenologically and quantitatively using LMF theory.