Mean-Square Nuclear Displacement ofFe57in Zn from the Mössbauer Effect

${\mathrm{Fe}}^{57}$ in Zn shows a quadrupole splitting of 0.53±0.03 mm/sec and a chemical shift of —0.53±0.02 mm/sec relative to an Fe metal absorber at room temperature. The measurements of the Mössbauer fraction $f$ indicate a ratio of mean-square displacements $\frac{{〈x^2〉}_{\parallel }}{{〈x^2〉}_{\perp }}>~2$ at room temperature relative to the crystal $c$ axis. This is in qualitative agreement with lattice-dynamical calculations.