A study on AB2O6 compounds, Part V: a DFT study on charge balance as driving force for structural organisation

In continuation of earlier investigations on the structures of AB(2)O(6) compounds we have remodelled those with A = Ca, Sr, Ba and B = As, Sb, V, Nb, Ta by relaxation in DFT calculations with the VASP code. The results match the real structures very closely. We have then calculated charges of the constituent atoms by means of a Bader analysis of the calculated electron density distribution. The results of these calculations are discussed with the aim to establish a correlation between the charges of the atoms and the vicinity structure around the atoms. Similar calculations were done first for all these compounds in a rosiaite type structure and second for CaAs2O6 in all the other structures found for these compounds. We discuss how the balance of charges changes on forcing the systems into another topology, and we finally address the issue that structural organisation is strongly determined by the need to balance charges of the constituting elements in their specific stoichiometric relation.