The all-electron first-principles discrete variational method was employed to study the electronic structure of ${\mathrm{SnF}}_4$, ${\mathrm{SnCl}}_4$, ${\mathrm{SnBr}}_4$, and ${\mathrm{SnI}}_4$. Values of the electronic density at the Sn nucleus were derived and related to ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ isomer shifts to obtain the nuclear constant Δ〈$r^2$〉. Differences in values of ρ(0) are discussed in terms of the chemical bonding between Sn and halogen atoms.

• Received 29 August 1988

DOI:https://doi.org/10.1103/PhysRevB.39.50