Direct route to reproducing pair distribution functions with coarse-grained models via transformed atomistic cross correlations

TL;DR

This paper introduces two non-iterative methods to directly parameterize coarse-grained models by adjusting atomistic cross correlations, improving the reproduction of structural features like pair distribution functions in complex liquids.

Contribution

The work presents novel direct approaches for coarse-grained model parametrization that better incorporate atomistic cross correlations without iterative fitting.

Findings

More accurate low-order structural features in CG models.

Enhanced reproduction of pair distribution functions in liquid water.

Insights into the role of cross-correlation features in structural accuracy.

Abstract

Coarse-grained (CG) models are often parametrized to reproduce one-dimensional structural correlation functions of an atomically-detailed model along the degrees of freedom governing each interaction potential. While cross correlations between these degrees of freedom inform the optimal set of interaction parameters, the correlations generated from the higher-resolution simulations are often too complex to act as an accurate proxy for the CG correlations. Instead, the most popular methods determine the interaction parameters iteratively, while assuming that individual interactions are uncorrelated. While these iterative methods have been validated for a wide range of systems, they also have disadvantages when parametrizing models for multi-component systems or when refining previously established models to better reproduce particular structural features. In this work, we propose two distinct approaches for the direct (i.e., non-iterative) parametrization of a CG model by adjusting the high-resolution cross correlations of an atomistic model in order to more accurately reflect correlations that will be generated by the resulting CG model. The derived models more accurately describe the low-order structural features of the underlying AA model, while necessarily generating inherently distinct cross correlations compared with the atomically-detailed reference model. We demonstrate the proposed methods for a one-site-per-molecule representation of liquid water, where pairwise interactions are incapable of reproducing the true tetrahedral solvation structure. We then investigate the precise role that distinct cross-correlation features play in determining the correct pair correlation functions, evaluating the importance of the placement of correlation features as well as the balance between features appearing in different solvation shells.