  Two intermetallic FeAl compounds with Al content of 70.68 and 72.17 at.pct
were studied using M\"ossbauer spectroscopy (5 to 296 K) and X-ray diffraction
(15 to 300 K). The compounds were found to crystallize in the orthorhombic Cmcm
space group (eta-phase). The collected data revealed that dynamics of the Fe
atoms (harmonic in entire temperature range) is significantly different that Al
atoms. For the latter strong anharmonicity was evidenced. Moreover, it was
found that partial filling of the different Al sites leads to occurrence of low
and high symmetry coordination of Fe atoms, which was reflected in occurrence
of two distinct doublets in M\"ossbauer spectra. All spectral parameters of the
doublets as well as the Debye temperature, force constant, kinetic and
potential energies of vibrations were determined. Those results revealed
significant differences between both alloys, likely originating from
approaching the stability boundary of the eta-phase for Fe-Al 72.17 at.pct
alloy.
