Mossbauer and X-ray diffraction studies of M1-xFex(PyNO)6(ClO4)2(M=Zn, Mg)

Abstract

Mossbauer and X-ray diffraction measurements have been made on M1-xFex(PyNO)6(ClO4)2, where M is Zn or Mg, for 0<x<or=1. It has been possible to reproduce the Mossbauer spectra reasonably well using a model in which the ferrous ions experience a small off-axial distortion from the nominal trigonal (C3i) site symmetry. The Mossbauer results indicate that the proportion of Fe2+ ions in sites that are distorted from trigonal symmetry varies as a function of iron concentration in the Zn-Fe series but remains apparently invariant across the Mg-Fe series. The unit-cell volume of these compounds was found to exhibit a strong non-linear dependence on composition for the Zn-Fe system, whereas a roughly linear relation was found for the Mg-Fe system. Furthermore, the behaviour of the unit-cell volume appears to be correlated with the composition-dependent changes in the proportion of ferrous ions distorted from C3i site symmetry.