Ab initio study of single-crystalline and polycrystalline elastic properties of Mg-substituted calcite crystals

作者：Zhu L F; Friak M^*; Lymperakis L; Titrian H; Aydin U; Janus A M; Fabritius H O; Ziegler A; Nikolov S; Hemzalova P; Raabe D; Neugebauer J

来源：Journal of the Mechanical Behavior of Biomedical Materials, 2013, 20: 296-304.

DOI：10.1016/j.jmbbm.2013.01.030

• Ab initio
• Calcite
• Stiffening
• Mg-substitution
• Elasticity

We employ ab initio calculations and investigate the single-crystalline elastic properties of (Ca,Mg)CO3 crystals covering the whole range of concentrations from pure calcite CaCO3 to pure magnesite MgCO3. Studying different distributions of Ca and Mg atoms within 30-atom supercells, our theoretical results show that the energetically most favorable configurations are characterized by elastic constants that nearly monotonously increase with the Mg content. Based on the first principles-derived single-crystalline elastic anisotropy, the integral elastic response of (Ca,Mg)CO3 polycrystals is determined employing a mean-field self-consistent homogenization method. As in case of single-crystalline elastic properties, the computed polycrystalline elastic parameters sensitively depend on the chemical composition and show a significant stiffening impact of Mg atoms on calcite crystals in agreement with the experimental findings. Our analysis also shows that it is not advantageous to use a higher-scale two-phase mix of stoichiometric calcite and magnesite instead of substituting Ca atoms by Mg ones on the atomic scale. Such two-phase composites are not significantly thermodynamically favorable and do not provide any strong additional stiffening effect.

• 出版日期2013-4