Calculation of lattice sums and the electric field gradients for the rhombic and tetragonal phases of YBa2Cu3Ox

The lattice sums are calculated on the basis of the point charge model and the values of the electric field gradients and asymmetry parameters η are determined for all cation sites of the orthorhombic and tetragonal phases of the superconductor YBa2Cu3Ox. The cases of different-valency copper at the Cu1 sites are considered separately. The values of the electric field gradients and η in the vicinity of local defects due to the different number and ordering of the oxygen vacancies at the Cu1 sites are calculated