Temperature dependence of the microscopic structure and density anomaly of the SPC/E and TIP4P-Ew water models. Molecular dynamics simulation results

TL;DR

This study uses molecular dynamics simulations to analyze how the microscopic structure and density of SPC/E and TIP4P-Ew water models change with temperature, revealing the link between hydrogen bonding and density anomalies.

Contribution

It provides a detailed temperature-dependent structural analysis of two popular water models, highlighting the role of hydrogen bonds in density maxima.

Findings

Maximum density correlates with the fraction of molecules with three and four bonds.

Temperature influences the dielectric constant of water models.

Structural changes are linked to supercooling behavior.

Abstract

We have investigated temperature trends of the microscopic structure of the SPC/E and TIP4P-Ew water models in terms of the pair distribution functions, coordination numbers, the average number of hydrogen bonds, the distribution of bonding states of a single molecule as well as the angular distribution of molecules by using the constant pressure molecular dynamics simulations. The evolution of the structure is put in correspondence with the dependence of water density on high temperatures down to the region of temperatures where the system becomes supercooled. It is shown that the fraction of molecules with three and four bonds determine the maximum density for both models. Moreover, the temperature dependence of the dielectric constant is obtained and analyzed.