Sternheimer valence shielding and antishielding factors for some ions of interest in Mossbauer spectroscopy

Abstract

Using nonrelativistic Hartree-Fock-Slater wave functions and Sternheimer's uncoupled perturbation-numerical method the valence shielding-antishielding factor R including exchange has been calculated for Cr, Mn⁺, Fe²⁺, Co³⁺, Ni⁴⁺ (all in 3d⁶ isoelectronic configuration), Ru²⁺ (4d⁶), Os²⁺ (5d⁶), Pr³⁺ (4f²), Tm³⁺ (4f¹²), and Np⁶⁺ (5f¹) to be 0.26, 0.15, 0.12, 0.10, 0.08, -0.06, -0.12, 0.12, 0.18, and 0.01, respectively. The quadrupole splitting data on Fe₂O₃, Al₂O₃·Fe³⁺, yttrium iron garnet (T_d and O_h Fe³⁺ sites), and FeSiF₆·6H₂O have been reinterpreted using more reliable values of Sternheimer shielding-antishielding factors to obtain Q(⁵⁷Fe^m) as 0.154, 0.179, 0.146, 0.139, and 0.156 b, respectively. The repercussions of the changes in the charge spread of the 3d⁶ ions in the crystalline lattice on R have also been discussed.