An ab-initio study of H2O adsorption on the calcite (104) surface with different coverages

Calcite is the most important component of limestone, an essential building material. When adsorbing water, the strength of calcite decreases, resulting in safety problems. Density functional theory (DFT) is widely used to elucidate the adsorption mechanisms of calcite surface at a molecular level. The adsorption structures and en- ergies of H2O on calcite (104) surface were studied systematically for a wide coverage from 0 to 1.0 monolayers. The results show that a hollow site on calcite (104) surface is the most favorable when adsorbing H2O with an energy of 0.89 eV, followed by 0.71 eV at the bridge site and 0.64 eV at the top site, i.e., water molecules are easily adsorbed on calcite surface. Besides, the changes in the atomic structure, density of electronic states, and charge distribution of H2O/calcite (104) system before and after adsorption are discussed in detail for different coverages.