Structural and dynamic properties of SPC/E water

TL;DR

This study uses molecular dynamics simulations to analyze how the structure and dynamics of SPC/E water change across temperatures from 213 K to 360 K, revealing increased order and hydrogen bonding at lower temperatures.

Contribution

It provides a detailed analysis of structural and dynamic properties of water using SPC/E model across a wide temperature range, highlighting the relationship between hydrogen bonding and water's behavior.

Findings

Structural order increases as temperature decreases.

Longer hydrogen bonds and caging effects dominate below 293 K.

Four hydrogen bonds per water molecule are prevalent at lower temperatures.

Abstract

I have investigated the structural and dynamic properties of water by performing a series of molecular dynamic simulations in the range of temperatures from 213 K to 360 K, using the Simple Point Charge-Extended (SPC/E) model. I performed isobaric-isothermal simulations (1 bar) of 1185 water molecules using the GROMACS package. I quantified the structural properties using the oxygen-oxygen radial distribution functions, order parameters, and the hydrogen bond distribution functions, whereas, to analyze the dynamic properties I studied the behavior of the history-dependent bond correlation functions and the non-Gaussian parameter alpha_2(t) of the mean square displacement of water molecules. When the temperature decreases, the translational (tau) and orientational (Q) order parameters are linearly correlated, and both increase indicating an increasing structural order in the systems. The probability of occurrence of four hydrogen bonds and Q both have a reciprocal dependence with T, though the analysis of the hydrogen bond distributions permits to describe the changes in the dynamics and structure of water more reliably. Thus, an increase on the caging effect and the occurrence of long-time hydrogen bonds occur below 293 K, in the range of temperatures in which predominates a four hydrogen bond structure in the system.