Water structure-forming capabilities are temperature shifted for different models

TL;DR

This study compares seven classical water models across a temperature range, revealing a universal structural pattern shift and linking model accuracy to the stabilization of fully coordinated water structures.

Contribution

It introduces a temperature shift analysis that aligns different water models' microscopic structural behaviors, providing a new comparison protocol.

Findings

All models share the same structural pattern up to a temperature shift.

Models reproducing the density maximum show more stabilized fully coordinated structures.

A master curve describes the structural behavior of all models after shifting.

Abstract

A large number of water models exists for molecular simulations. They differ in the ability to reproduce specific features of real water instead of others, like the correct temperature for the density maximum or the diffusion coefficient. Past analysis mostly concentrated on ensemble quantities, while few data was reported on the different microscopic behavior. Here, we compare seven widely used classical water models (SPC, SPC/E, TIP3P, TIP4P, TIP4P-Ew, TIP4P/2005 and TIP5P) in terms of their local structure-forming capabilities through hydrogen bonds for temperatures ranging from 210 K to 350 K by the introduction of a set of order parameters taking into account the configuration of the second solvation shell. We found that all models share the same structural pattern up to a temperature shift. When this shift is applied, all models overlap onto a master curve. Interestingly, increased stabilization of fully coordinated structures extending to at least two solvation shells is found for models that are able to reproduce the correct position of the density maximum. Our results provide a self-consistent atomic-level structural comparison protocol, which can be of help in elucidating the influence of different water models on protein structure and dynamics.