Investigation of the interaction of water with the calcite {1014} surface using ab-initio simulation

Density functional theory calculations were employed to explore the interaction between water and the (10.4) surface of calcite. Static relaxations of both associated and dissociated H2O molecules revealed the latter to be energetically unfavorable, with the metastable dissociated state 1.77 eV higher in energy than the associated state. Ab initio molecular dynamics (MD) simulations of low water coverage revealed fluctuations in the H−Owater bond, which were especially prominent when an H atom was directed toward a surface CO3. Desorption of the H2O occurred in simulations above 900 K. During an MD simulation of 100% water coverage, the H2O molecules arranged themselves into a zigzag pattern flat on the surface. As coverage was increased further, to 200%, the H2O molecules formed three layers of water; the lower molecules lay flat on the surface, while the upper molecules were split between those interacting with the surface and those interacting with other H2O molecules.