Charge states of atoms in HgBa2CuO4 and HgBa2CaCu2O6 lattices

Mössbauer emission spectroscopy on the ⁶⁷Cu(⁶⁷Zn) isotope has been used to determine the parameters of the electric-field gradient tensor at the copper sites of the HgBa₂Ca _n?1Cu_nO_2n+2 lattices (n=1,2), as well as to calculate these parameters in the point-charge approximation. An analysis of the results, combined with available NQR literature data for the ⁶³Cu isotope, has shown that the best fit of calculated to experimental data can be reached by assuming that the holes due to the presence of defects in the material localize primarily in the sublattice of the oxygen lying in the copper plane.