Research of cation dependences of structural and elastic properties of metal carbonates series by density functional theory calculations

Using the density functional theory methods with the PBE gradient functional, and taking into account the van der Waals interaction in the basis of localized atomic orbitals, using the CRYSTAL 17 program code, calculations of the structure and elastic constants for MgCO3, ZnCO3, CdCO3 CaCO3 in the calcite structure, CdMg(CO3)(2), CaMg(CO3)(2), CaZn(CO3)(2) in the dolomite structure, BaMg(CO3)(2) - norsethite, and CaCO3, SrCO3, PbCO3, BaCO3 in the aragonite structure are calculated. It is shown that the lattice constants, interatomic distances linearly depend on the cation radius R-M, and the band gap, atomic charges, overlap populations of electron shells, and crystal density depend on cation electronegativity chi(M). Elastic compression constants and linear elastic moduli along the c axis are also described by R-M. For polycrystalline bulk modulus B-H, shear modulus G(H), and Young's modulus EH, linear dependences with a good correlation coefficient were obtained: B-H (GPa) = 175.95-84.89.R-M, G(H) (GPa) = 87.57-46.05.R-M, E-H (GPa) = 224.36-103.59.R-M. Similar dependences are established for the longitudinal and transverse speeds of sound, the Debye temperature and the coefficient of minimum thermal lattice conductivity. These results can be used to predict the elastic and mechanical characteristics of carbonates with the chemical formula MCO3 and solid solutions based on them.