Theoretical equilibrium and growth morphologies of CaCO3 polymorphs: Aragonite and calcite

The work concerns the theoretical equilibrium and growth morphologies of the two main polymorphs of the calcium carbonate: calcite and aragonite. By applying the Periodic Bond Chain analysis and using potential functions tailored on physical properties of both these polymorphs, the anisotropy of surface properties is represented as close as possible. As concerns the equilibrium form, the reasonable mean value of 950 erg cm(-2) is obtained for specific surface energy of aragonite. The growth habits are compared with those of natural crystals; the more or less striking discrepancies can be mainly ascribed to water adsorption, at least for the most important forms. This is made possible by the information gained analysing the gypsum/aragonite epitaxy.