Calibration of the isomer shift for the14.4−keVtransition inFe57using the full-potential linearized augmented plane-wave method

Abstract

Full-potential linearized augmented plane-wave method has been used to calibrate isomer shift for the $14.4\text{\ensuremath{-}}\mathrm{keV}$ resonant transition in $^{57}\mathrm{Fe}$. Augmented plane waves and local orbitals were used for the valence electrons. For the correlation and exchange potentials, a generalized gradient approximation has been adopted. Calculations have been performed for the following compounds: $\mathrm{Fe}{\mathrm{F}}_{2}(P{4}_{2}∕mnm)$, $\mathrm{Fe}{\mathrm{Cl}}_{2}(R\overline{3}m)$, $\mathrm{Fe}{\mathrm{Br}}_{2}(P\overline{3}m1)$, $\mathrm{Fe}{\mathrm{I}}_{2}(P\overline{3}m1)$, $\mathrm{Fe}{\mathrm{F}}_{3}(R\overline{3}c)$, $\mathrm{Ti}\mathrm{Fe}(Pm\overline{3}m)$, and $\mathrm{Fe}(Im\overline{3}m)$. Strong on-site Coulomb interactions in the $\mathrm{Fe}\phantom{\rule{0.2em}{0ex}}3d$ shell of halides were taken into account by applying the Hubbard repulsion parameter $U$ and the on-site exchange interaction constant $J$. The isomer shift calibration constant of $\ensuremath{\alpha}=\ensuremath{-}0.291\phantom{\rule{0.3em}{0ex}}{\mathrm{a.u.}}^{3}\phantom{\rule{0.2em}{0ex}}\mathrm{mm}\phantom{\rule{0.2em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ has been obtained. The nuclear quadrupole moment of the excited nuclear state involved was found to be $Q=+0.17\phantom{\rule{0.3em}{0ex}}\mathrm{b}$.