We have measured the total shift of the Mössbauer spectra of the intermetallic compounds ErFe2 and ZrFe2 from 293 K to 700 K. We have made several assumptions in the separation of the total shift in order to extract the dynamical properties of the iron sub-assembly. We have proved that at high temperature, the temperature shift seems to be intensitive to the details of the vibrational systems and at very high temperatures it approaches asymptotically to the classical value. We extracted the so-called Debye frequencies for this sub-assembly and found to be too big. We made further assumptions using our X-ray data and the connection between the magnetic and vibrational properties of the system, which seems to account for the discrepancies that we first found.