Structure and Dynamics of the TIP3P, SPC, and SPC/E Water Models at 298 K

TLDR

Empirical three‑site water models differ in Lennard‑Jones and Coulombic parameters, leading to notable variations in self‑diffusion coefficients and the second peak of gOO. The authors performed nanosecond NVE molecular dynamics simulations of 901 water molecules in a cubic cell with periodic boundaries using CHARMM, applied SHAKE to constrain rigid molecules, and calculated self‑diffusion coefficients and radial distribution functions for five three‑site water models, comparing them to experimental data and assessing the impact of velocity rescaling.

Abstract

Molecular dynamics simulations of five water models, the TIP3P (original and modified), SPC (original and refined), and SPC/E (original), were performed using the CHARMM molecular mechanics program. All simulations were carried out in the microcanonical NVE ensemble, using 901 water molecules in a cubic simulation cell furnished with periodic boundary conditions at 298 K. The SHAKE algorithm was used to keep water molecules rigid. Nanosecond trajectories were calculated with all water models for high statistical accuracy. The characteristic self-diffusion coefficients D and radial distribution functions, gOO, gOH, and gHH for all five water models were determined and compared to experimental data. The effects of velocity rescaling on the self-diffusion coefficient D were examined. All these empirical water models used in this study are similar by having three interaction sites, but the small differences in their pair potentials composed of Lennard-Jones (LJ) and Coulombic terms give significant differences in the calculated self-diffusion coefficients, and in the height of the second peak of the radial distribution function gOO.