First principles calculations of oxygen vacancy formation in barium-strontium-cobalt-ferrite

The flexoelectricity of barium and strontium titanates from first principles.

We present ab initio calculations of the longitudinal flexoelectricity for BaTiO(3) and SrTiO(3) using a direct approach. The calculated value for SrTiO(3) agrees with recently reported measurements. For BaTiO(3), however, the theoretical values are smaller than the measured ones; possible reasons for the discrepancy are discussed.

R-Ferrite-type barium cobalt stannate, BaCo2Sn4O11

BaCo(2)Sn(4)O(11) is isotypic with R-ferrite, BaTi(2)Fe(4)O(11). The Co atoms fully occupy trigonal-bipyramidal sites () and are disordered with Sn atoms in octa-hedral sites (.2/m symmetry), as represented in the formula BaCoSn(2)(Co(0.34)Sn(0.66))(4)O(11). Ba atoms are situated in a 12-fold coordinated site ( symmetry).

First-principles calculations of the vacancy formation energy in transition and noble metals

First principles study of oxygen vacancy defects in tantalum pentoxide

First principles total energy calculations were performed to characterize oxygen vacancy defects in tantalum pentoxide (Ta2O5). A simplified version of the crystalline orthorhombic phase of Ta2O5 was used in this study. Results indicate that O vacancies in Ta2O5 can be broadly classified based on their location in the lattice. One type of vacancy that occupies the ‘‘in-plane’’ sites displays de...

First principles study of oxygen vacancy migration in tantalum pentoxide

First principles total energy calculations were performed in order to determine oxygen vacancy migration energies in Ta2O5 . A simplified version of the crystalline orthorhombic phase of Ta2O5 was used in this study. O vacancies in the chosen model of Ta2O5 can be broadly classified into ‘cap’ and ‘in-plane’ sites based on their location in the lattice. The cap type of vacancies display the lar...