Structural and dynamic properties of SPC/E water

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 $\sim$ 293 K, in the range of temperatures in which predominates a four hydrogen bond structure in the system.

Received: 13 July 2009, Revised: 29 December 2009, Accepted: 7 February 2010; Edited by: S. A. Cannas; Reviewed by: P. Netz, Inst. de Química, Univ. Federal do Rio Grande do Sul, Brazil; DOI: 10.4279/PIP.020001