Molecular Dynamics Study of Diffusion of Argon in Water at Different Temperatures

Abstract

Molecular dynamics study of a binary mixture of argon and SPC/E water, with argon as solute and water as solvent, at argon mole fraction of 0.023 have been accomplished at temperatures 293 K, 298 K, 303 K, 308 K and 313 K. The solvent-solvent, solute-solute and solute-solvent radial distribution functions (RDFs) have been estimated. The water-water radial distribution function has been found to agree with the experimental values within 5%. Self-diffusion coefficients of both solvent and solute have been determined by means of mean-squared displacement (MSD)curves using Einstein’s relation. The evaluated selfdiffusion coefficient at temperature 298 K has been found to agree with the experimental value within 4%. Also the values of self-diffusion coefficient of water have been found to agree with the available experimental values within 8% at maximum. Then, the Darken’s relation has been invoked in order to determine the mutual/binary diffusion coefficients at the respective temperatures. The temperature dependence of the diffusion coefficients has also been analyzed. The estimated values of self-diffusion coefficients of water and argon as well as the mutual diffusion coefficients of argon in water have given the linear Arrhenius plot, which indicates that the self-diffusion coefficients have an Arrhenius dependence on temperature. Moreover, the temperature dependence of the diffusion coefficients has been found to be consistent with the nature of RDF’s at the respective temperatures