Atomistic computer modeling of the crystal-morphology of corundum group minerals

Gromalova N. A., Eremin N. N., Urusov V. S.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 4. P. 84-92

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Language: Russian

Abstract

The partly ionic potential of the inter-atomic interaction had been chosen for atomistic calculations which have allowed to describe correctly structural, elastic and thermodynamic characteristics of corundum Al₂O₃, eskolaite Cr₂O₃ and hematite Fe₂O₃. These techniques had been successfully applied in modeling intermixture properties and the local structure of the solid solution (Al,Cr,Fe)₂O₃ (Eremin et al., 2008) and, thus, was used for analysis of thermodynamically equilibrium habits of these trioxides and their comparison with real facing of natural samples. Results obtained in the present study have been compared with other atomistic calculations in the ionic-shell modeling (Lawrence, Parker, 1988; De Leew et al., 1999; De Leew, Parker, 1999), ab-initio calculations in LDA and GGA approximations (Manassidis, Gillian, 1994; Marmier, Parker, 2004), as well as with experimental studies of crystallomorphology of natural compounds on the base of corundum (Minerals, 1972; Choi et al., 1997; Kitayama, Glaeser, 2004). Despite the similarity of theoretically calculated and natural parameters of crystals, there is a divergence between their morphological series, and the great influence of admixtures is evident for natural samples — just admixtures are responsible there for the natural crystal habit. Reconstruction of the equilibrium habit of crystals shows that the principal factor, determining the calculated surface energy value, is the correct assignment of the modeled potentials. For instance, surface energy of the face {110} in corundum crystal varies in value from 1 to 15 % depending on the chosen model.

Key words: atomistic modeling, morphology, corundum, eskolaite, hematite.