The structure and oscillational motion of 57Fe atoms in interstitial sites in Al as determined from interference of Mössbauer γ radiation

The first excited site of the ⁵⁷Fe atom entrapped in an interstitial site in aluminum, as reported by W. Petry, G. Vogl, and W. Mansel (Phys. Rev. Lett.45, 1862 (1980)). from a Mössbauer spectroscopic study of a single crystal, is analyzed by consideration of the value of the Hooke's law constant of the FeAl bonds obtained from the values for elemental Fe and Al. The eight wavefunctions for the eightfold nearly degenerate excited state are described as 2s1p1d1f hybrids of three-dimensional harmonic oscillator wavefunctions relative to the center of the undistorted Al₆ octahedron or as localized 1s functions relative to the center of the distorted octahedron. These considerations provide a qualitative understanding of the observations on this system.