Computer simulations of NaCl association in polarizable water

Abstract

Classical molecular dynamics computer simulations have been used to investigate the thermodynamics and kinetics of sodium chloride association in polarizable water. The simulations make use of the three-site polarizable water model of Dang [J. Chem. Phys. 97, 2659 (1992)], which accurately reproduces many bulk water properties. The model’s static dielectric constant and relaxation behavior have been calculated and found to be in reasonable agreement with experimental results. The ion–water interaction potentials have been constructed through fitting to both experimental gas-phase binding enthalpies for small ion–water clusters and to the measured structures and solvation enthalpies of ionic solutions. Structural properties and the potential of mean force for sodium chloride in water have been calculated. In addition, Grote–Hynes theory has been used to predict dynamical features of contact ion-pair dissociation. All of the calculated ionic solution properties have been compared with results from simulations using the extended simple point charge (SPC/E), nonpolarizable water model [J. Phys. Chem. 91, 6296 (1987)]. The dependence on polarizability is found to be small, yet measurable, with the largest effects seen in the solvation structure around the highly polarizable chlorine anion. This work validates the use of some nonpolarizable water models in simulations of many condensed-phase systems of chemical and biochemical interest.

Effects of Cations on the Hydrogen Bond Network of Liquid Water: New Results from X-ray Absorption Spectroscopy of Liquid Microjets

“…33 However, the distribution of angles from classical MD simulations (such as the one used here to obtain the cluster geometries) tends to be strongly peaked at 180°and decreases to near zero by 90°, although the details depend importantly on the particular simulation force field used. 24,33,39,40 Thus, the orientation of water molecules with respect to the cation in the clusters used here (obtained from classical MD simulations) may not provide a completely accurate representation of the relative orientations between the diValent cations and the solvating water molecules. However, these calculations should provide a reasonable first approximation of the direct electronic perturbation by the divalent cations.…”

Systematic comparison of force fields for microscopic simulations of NaCl in aqueous solutions: Diffusion, free energy of hydration, and structural properties

“…Description of ions is thus only a small part of their capabilities. For comparison, we have included one hand-optimised set of parameters for NaCl only [15].…”

“…For NaCl we used Gromacs, Charmm-22/x-plor, Charmm-27, Amber-1999 and OPLS-AA force fields, and the parametrisation by Smith and Dang [15]. The water models used for the aqueous solution were SPC, SPC/E, TIP3P and TIP4P.…”

Small Details Matter: The 2′-Hydroxyl as a Conformational Switch in RNA

“…All profiles were obtained in water as simulated by the IEFPCM continuum method. 14 Analysis of electron distribution using Bader's atoms in molecules (AIM) theory [15][16][17] was performed on reduced clusters representative of the most prevalent orientations of the κ angle (three replicas per relevant  orientation). Single-point calculations at the MP2(FC)/6-31G(d,p) level were performed at the dinucleotide level, removing the base at 3' and completing the valence of the C1', O5', and O3' atoms with H atoms.…”