title: Ab initio study of single-crystalline and polycrystalline elastic properties of Mg-substituted calcite crystals.
abstract: 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.
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, Düsseldorf 40237, Germany.
authors.forename: L-F
authors.initials: LF
authors.lastname: Zhu
authors.forename: M
authors.initials: M
authors.lastname: Friák
authors.forename: L
authors.initials: L
authors.lastname: Lymperakis
authors.forename: H
authors.initials: H
authors.lastname: Titrian
authors.forename: U
authors.initials: U
authors.lastname: Aydin
authors.forename: A M
authors.initials: AM
authors.lastname: Janus
authors.forename: H-O
authors.initials: HO
authors.lastname: Fabritius
authors.forename: A
authors.initials: A
authors.lastname: Ziegler
authors.forename: S
authors.initials: S
authors.lastname: Nikolov
authors.forename: P
authors.initials: P
authors.lastname: Hemzalová
authors.forename: D
authors.initials: D
authors.lastname: Raabe
authors.forename: J
authors.initials: J
authors.lastname: Neugebauer
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D002119:Calcium Carbonate / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D055119:Elastic Modulus; D008274:Magnesium / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D001672:Biocompatible Materials; D002119:Calcium Carbonate; D008274:Magnesium