A Monte Carlo simulation on structure and thermodynamics of potassium nitrate electrolyte solution

Abstract

Monte Carlo computer simulation of potassium nitrate solution is carried out in the concentration ranging from 0.3 to 7.0 mol l⁻¹. The cation (K⁺) and solvent water molecules are regarded as the charged and dipolar hard sphere respectively, and a simple four-site model for the nitrate ion is adopted in this study. It is found that there is an abrupt decline in the pressure with increasing ion concentration at fixed temperature. In supersaturated solutions for temperatures of 303 and 333 K, a metastable state with negative pressures and a strong energy fluctuation are observed. Some large ionic clusters are observed in supersaturated solutions at a temperature of 333 K, and they are composed of an ionic chain with alternating sign which indicates the formation of crystallization morphology. With decreasing solution concentration, the ionic hydration number varies from 5–7 for cation K⁺ and 3.5–4.7 for anion NO

, which is in good agreement with time-of-flight neutron diffraction results.

Acknowledgement

This work is supported by Natural Science Foundation of China (No. 20076001 and No. 20236010).