On the relation between hydrogen bonds, tetrahedral order and molecular mobility in model water

TL;DR

This study uses molecular dynamics simulations to explore how hydrogen bond lifetime, tetrahedral order, and molecular mobility are interrelated in different water models, especially at low temperatures.

Contribution

It compares four water models, highlighting the impact of explicit lone pairs on hydrogen bonding, tetrahedral order, and diffusion at various temperatures.

Findings

Models with explicit lone pairs show longer hydrogen bond lifetimes.

Explicit lone pair models exhibit better tetrahedral order.

Models with lone pairs have lower diffusion coefficients at low temperatures.

Abstract

We studied by molecular dynamics simulations the relation existing between the lifetime of hydrogen bonds, the tetrahedral order and the diffusion coefficient of model water. We tested four different models: SPC/E, TIP4P-Ew, TIP5P-Ew and Six-site, these last two having sites explicitly resembling the water lone pairs. While all the models perform reasonably well at ambient conditions, their behavior is significantly different for temperatures below 270 K. The models with explicit lone-pairs have a longer hydrogen bond lifetime, a better tetrahedral order and a smaller diffusion coefficient than the models without them.