Bulk and surface properties of gypsum: A comparison between classical force fields and dispersion-corrected DFT calculations

Abstract

A crucial step in atomistic simulations of interfacial phenomena is confirming the thermodynamic consistency of the force field. This can be achieved by investigating the ability of the force field in predicting the bulk and surface properties of all components in the system. In this work, our focus is on the interfacial properties of gypsum, the calcium sulfate dihydrate (CaSO4·2H2O), which is the most abundant calcium sulfate in the earth crust. The performance of classical force fields was tested by comparing their results with those calculated with dispersion-corrected density functional theory (DFT-D) method as well as experimentally reported data. The DFT-D method implemented to study gypsum and showed a promising performance by reproducing experimentally reported bulk and surface properties. We showed that properties calculated using classical force fields are highly dependent on ionic partial charges. Substituting the original ionic partial charges in the CLAYFF force field with those of the INTERFACE force field improved the calculated bulk and surface properties significantly. CLAYFF with augmented partial charges and INTERFACE force fields showed the best overall performance in reproducing bulk and surface properties of gypsum.