Mössbauer isomer shifts inZn++67andNi++61nuclei

Mössbauer charge density for ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}_{}^{++}{}_{}{}^{} \left(3\mathrm{}{d}^8\right)$ is calculated using Hartree-Fock wave functions. All the core $s$ functions ${\phi }_{\mathrm{ns}} (n=1,2, \mathrm{and} 3)$ of ${\mathrm{Ni}}^{++}$ and their overlaps with six ${\mathrm{O}}^{--}$ arranged in an octahedron corresponding to NiO are calculated as a function of interatomic distance $R$. Similar calculations for ${}_{}{}^{67}{}_{}{}^{}\mathrm{Zn}_{}^{++}{}_{}{}^{}$ in a tetrahedral environment of ${\mathrm{O}}^{--}$ ions, appropriate to ZnO, are also performed. It is found that the isomer shift is given approximately by a "power law" $\sim R^{-7\mathrm{}}$.