Ab initioDetermination ofFem57Quadrupole Moment from Mössbauer Data

Abstract

A new determination of the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}_{}^m{}_{}{}^{}$ quadrupole moment has yielded the value 0.082 b, which is only half of the currently accepted value. The procedure combined first-principles calculation of the field gradients at the Fe nucleus in Fe${\mathrm{Cl}}_2$ and Fe${\mathrm{Br}}_2$ molecules with published quadrupole splittings for those molecules trapped in rare-gas matrices. The field gradients are strongly influenced by iron $3p$ covalency.