A Computational Investigation of Aragonite/Dolomite Epitaxy

We studied several aragonite/dolomite interfaces through empirical calculations in the present work. To establish the most favorable epitaxy relationships between aragonite (Arg) and dolomite (Dol), the adhesion energies at 0 K (i.e., the energy released when two phases are brought into contact along a given interface) of different (hkl)Arg/(h’k’.l’)Dol interfaces were calculated. The effect of the Mg2+-Ca2+ order/disorder of the dolomite structure on the stability of the aragonite/dolomite interfaces was also evaluated. Based on our calculations, we suggest that aragonite may have played a crucial role in dolomite formation in some past geological contexts. Precipitation of metastable aragonite in seawater may have acted as a substrate to trigger dolomite formation, lowering the activation energy for its nucleation (i.e., heterogeneous nucleation of dolomite on aragonite). We also suggest that the {001} form of aragonite, observed in crystals grown in Mg2+-rich aqueous solution, could be stabilized by the deposition of some layers of disordered dolomite in epitaxial relationship with (001)Arg (i.e., 2D epitaxy as a habit modifier).