Computational Approach to the Study of Epitaxy: Natural Occurrence in Diamond/Forsterite and Aragonite/Zabuyelite

In this contribution the theoretical and computational aspects related to the determinations of the (i) interface structure, (ii) adhesion energy, and (iii) interfacial energy of a system composed by two crystalline phases in epitaxial relationship are discussed. Specifically, we describe the possible 2D lattice coincidences between two phases in epitaxial relationship, as well as all of the possible initial interface configurations which generate when different surface terminations of the phases put in contact are taken into account. Then, in order to elucidate these theoretical aspects, we have studied the following epitaxies in natural systems: {110}-diamond (C)/{101}-forsterite (Mg2SiO4) and {001}-aragonite (CaCO3)/{1̅01}-zabuyelite (Li2CO3); the optimized interface structures and their adhesion energies were determined at the ab initio level. For the diamond/forsterite system, a very low value of the adhesion energy was estimated, β(110)/(101) D/Fo = 0.367 J/m2, suggesting a low probability to have epitaxy between {110}-diamond and {101}-forsterite. A higher adhesion energy was instead found for the aragonite/zabuyelite system, β(1̅01)/(001) Za/Ar = 0.595 J/m2, which reveals a strong affinity between the {1̅01}-zabuyelite and {001}-aragonite.