Reconstruction of the {101¯4} Calcite Surface: When, How, and Why

Using density functional theory (DFT) we have successfully determined the conditions under which {101¯4} calcite surface reconstruction occurs in vacuum and in water. Ab initio lattice dynamics and molecular dynamics were used to confirm that reconstruction, as observed in previous experimental and modeling studies, occurs when the surface is in vacuum, though transitions of unreconstructed sites to reconstructed sites and vice versa is observed at temperatures >200 K. Hydrogen bonding between water and carbonate anions inhibits site reconstruction. For this reason, wet surface reconstruction is observed at any temperature only when the surface is covered with half a layer of water molecules that occupy unreconstructed sites. This work highlights that calcite surface reconstruction is likely to occur under certain low-pressure gas phase conditions, but not at the interface with liquid water.