Affiliation:
1. Max-Planck-Institut für Eisenforschung GmbH
2. University of Ulm
3. Bulgarian Academy of Sciences
Abstract
We use quantum-mechanical calculations to study single-crystalline elastic properties of (Ca,Mg)CO3crystals with concentrations ranging from calcite CaCO3to magnesite MgCO3. By analyzing results for a dense set of distributions of Ca and Mg atoms within 30-atom supercells, our theoretical study shows that those atomic configurations, that minimize the total energy for a given concentration, are characterized by elastic constants that either increase with the Mg content or remain nearly constants. Employing theseab initiocalculated single-crystalline elastic parameters, the polycrystalline elastic properties of (Ca,Mg)CO3aggregates are determined using a mean-field self-consistent homogenization method. The computed integral elastic moduli (bulk and shear) show a significant stiffening impact of Mg atoms on calcite crystals. Our analysis also demonstrates that it is not advantageous to use a granular two-phase composite of stoichiometric calcite and magnesite instead of substituting individual Ca and Mg atoms. Such two-phase aggregates are not significantly thermodynamically favorable and do not offer any strong additional stiffening effect.
Publisher
Trans Tech Publications, Ltd.
Subject
Mechanical Engineering,Mechanics of Materials,General Materials Science
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