Investigation of hydration of potassium carbonate via reactive force-field molecular dynamics simulations

A reactive force field potential was applied to H2O/K2CO3 systems, and its effectiveness was verified through first-principles calculations and experimental data. Thereafter, molecular dynamics simulations were conducted to investigate the sorption of water molecules onto the K2CO3 (001) surface for water coverages from 0.5-3.0 monolayers (ML) at 0.5-ML intervals. As the water coverage was increased, the water molecule order on the K2CO3 (001) surface decreased, the number of water layers changed from one to three, and some water molecules passed through the first atomic layer of the surface while interacting with the second/third ones. Owing to the differences in water-surface and water-water interactions, the minimum and maximum self-diffusion coefficients appeared at 0.5 ML and 1.0 ML, respectively. At high water coverage, temperature negatively affected water molecule sorption, indicating that reduced temperatures improved the sorption properties of the H2O/K2CO3 (001) system. Two types of hydrogen bonds-those between water and the surface (HB1) and those between water molecules (HB2)-were formed in the H2O/K2CO3 (001) system, and they competed with each other in water sorption on the K2CO3 (001) surface. For practical applications, the formation of HB1- and HB2-type hydrogen bonds should be promoted and inhibited, respectively, to improve the sorption effects and avoid hydrolysis.