Modeling the lattice parameters of zircon-type MXO4 (M=divalent, trivalent or tetravalent metal, X=V, P, As, Si) crystals

The relations between the crystal lattice parameters and the properties of the constituting ions in a group of 109 compounds with the general formula MXO4 (M stands for a divalent, trivalent or tetravalent metal, and X=V, P, As, Si) having the zircon-type structure are considered in the present paper. It was shown that both a and c lattice parameters are linear functions of the sum of ionic radii and difference of electronegativities of the M ions and oxygen. The mean relative error between the experimental and modeled crystal lattice parameters is only about 0.23%. The linear equations of the model can be readily applied to estimate the lattice parameters of new compounds with the same crystal structure. Several two-dimensional diagrams plotted for certain combinations of the properties of constituting ions and experimental lattice constants suggest criteria of stability for the considered zircon-type structure

Ab Initio Calculations of the Structural and Electronic Properties of Ca2La3Sb3O14 Weberite at Ambient and Elevated Hydrostatic Pressure

The structural and electronic properties of the Ca2La3Sb3O14 were calculated for the first time using the density functional theory (DFT) methods. The material crystallizes in the weberite structure. The optimized crystal structure constants are in good agreement with the experimental findings. The calculated direct bandgap was 1.864 eV (in the generalized gradient approximation) and 2.443 eV (in the local density approximation). The bulk modulus values obtained from the pressure dependence of the optimized unit cell volume were 128.72 GPa (GGA) and 158.56 GPa (LDA), respectively. Influence of the hydrostatic pressure on the structural and electronic properties was also examined in in this work

Crystal field parameters and energy level structure of the MnO43 12 tetroxo anion in Li3PO4, Ca2PO4Cl and Sr5(PO4)3Cl crystals

A comparative study concerning the electronic structure of the Mn5+ ion in the Li3PO4, Ca2PO4Cl, Sr-5(PO4)(3)Cl host lattices has been carried out in the framework of the exchange charge model. The crystal field parameters have been evaluated using the structural data as the only input information. The 10 K absorption spectra of the investigated compounds have been measured in order to verify the correspondence between experimental and calculated energy levels. A systematic trend of the crystal field splitting of the most intense transitions has been evidenced and discussed by considering the symmetry properties of the coordination polyhedra around Mn5+

Spin-Hamiltonian Parameters For CrLi3+ Doped In LiNbO3

By using crystal field theory, the spin-Hamiltonian parameters [zero-field splitting D, the giromagnetic factors g (g|| and g⊥) and the first excited state splitting δ(2E)] for the CrLi3+ doped in LiNbO3 have been calculated from the higher-order perturbation formulas. The method used is based on the two-spin-orbit coupling parameter model, in a cluster approach. The g parameters were also calculated as a second derivative of the energy, method implemented into ORCA computer program. The results were discussed and good agreement with experimental data was demonstrated