ReaxFF molecular dynamics simulations of electrolyte-water systems at supercritical temperature

Nabankur Dasgupta; Yun Kyung Shin; Mark V Fedkin; Adri van Duin

doi:10.1063/5.0006676

ReaxFF molecular dynamics simulations of electrolyte-water systems at supercritical temperature

J Chem Phys. 2020 May 29;152(20):204502. doi: 10.1063/5.0006676.

Authors

Nabankur Dasgupta¹, Yun Kyung Shin², Mark V Fedkin², Adri van Duin¹

Affiliations

¹ Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
² Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.

PMID: 32486685
DOI: 10.1063/5.0006676

Abstract

We have performed ReaxFF molecular dynamics simulations of alkali metal-chlorine pairs in different water densities at supercritical temperature (700 K) to elucidate the structural and dynamical properties of the system. The radial distribution function and the angular distribution function explain the inter-ionic structural and orientational arrangements of atoms during the simulation. The coordination number of water molecules in the solvation shell of ions increases with an increase in the radius of ions. We find that the self-diffusion coefficient of metal ions increases with a decrease in density under supercritical conditions due to the formation of voids within the system. The hydrogen bond dynamics has been interpreted by the residence time distribution of various ions, which shows Li⁺ having the highest water retaining capability. The void distribution within the system has been analyzed by using the Voronoi polyhedra algorithm providing an estimation of void formation within the system at high temperatures. We observe the formation of salt clusters of Na⁺ and K⁺ at low densities due to the loss of dielectric constants of ions. The diffusion of ions gets altered dramatically due to the formation of voids and nucleation of ions in the system.