Quadrupole antishielding factors and polarizabilities in ionic crystals

Abstract

Using nonrelativistic Hartree-Fock-Slater wave functions and Sternheimer's perturbation-numerical method, the quadrupole antishielding factor γ_∞ and quadrupole polarizability aq have been calculated for 35 free ions isoelectronic with He, Ne, Ar, Kr, Xe, and Rn configurations. Assuming an additional potential due to a charged hollow sphere of Watson type around the ion in crystals, the self-consistent wave functions for 10 additional negative ions O²⁻, S²⁻, Se²⁻, Te²⁻, P³⁻, As³⁻, Sb³⁻, Si⁴⁻, Ge⁴⁻, and Sn⁴⁻ have been generated in order to calculate γ_∞ and aq for a total of 45 closed-shell ions in crystals. In the presence of the spherical potential, the negative-ion γ_∞ and α_q values decrease while the positive-ion values increase as compared to the corresponding free-ion values, respectively. The effect of contraction of wave functions on γ_∞ and α_q for singly and doubly negative ions has been studied as a function of the radius of the hollow sphere over a range of values around the Pauling ionic radius and in each case a satisfactory polynomial relationship has been assigned.