Molecular dynamics simulations of the incorporation of Mg 2+ , Cd 2+ and Sr 2+ at calcite growth steps: Introduction of a SrCO 3 potential model

Abstract

Molecular dynamics simulations were used to model the incorporation of magnesium, cadmium and strontium ions at two stepped (10 1 4) surfaces of the calcium carbonate polymorph calcite. The potential model used in the simulations was derived to reproduce experimental enthalpies of CaCO 3 , MgCO 3 , CdCO 3 and SrCO 3 formation and dissolution and the effect of solvent was modelled by the addition of a layer of water molecules. From the calculated energies we expect that, in a solution containing all four cations, MgCO 3 and SrCO 3 grow onto the calcite steps in preference to CdCO 3 and especially CaCO 3 . Growth of complete rows of MgCO 3 and CdCO 3 occurs at either step edge, while growth of a row of SrCO 3 at the acute edge releases a large amount of energy ( m 420 kJ mol m 1 ), which should, therefore, be the preferential step for incorporation of complete SrCO 3 edges.

Keywords:

• Calcite
• Computer Simulation
• Impurities
• Growth
• Inhibition