Examining the Hydration Behavior of Aqueous Calcium Chloride (CaCl₂) Solution via Atomistic Simulations

Abstract

Equilibrium molecular dynamics simulations are performed to examine the hydration behavior of Ca2+ and Cl− across a wide range of salt concentrations (from 1 wt.% to 60 wt.% CaCl2) in an aqueous solution. The predicted radial distribution functions (RDFs) and coordination numbers (CNs) of Ca2+–water, Cl−–water, and Ca2+–Cl− agree with the previous studies conducted at concentrations below the solubility limit at room temperature. The hydration limit of aqueous calcium chloride solution is identified at 10 wt.% CaCl2 as the CNs remain constant below it. Beyond the bulk solubility limit ~44.7 wt.% CaCl2, a noticeable decrease in the CN of Cl− and water is recorded, implying the saturation of the solution. The solvating water molecules decrease with increasing salt concentration, which can be attributed to the growth in the number of ion pairs.

Keywords

• hydration
• molecular dynamics
• salt solution
• solubility