Studies on mixed metal(II)–iron(II) chloride systems. Part 1. Mössbauer and X-ray powder diffraction data for MxFe1–xCl2·4H2O (M = Mn, Co, or Ni; x= 0–0.75) systems

Abstract

The ⁵⁷Fe Mössbauer data of the phases M_xFe_1–xCl₂·4H₂O (M = Mn, Co, or Ni; x= 0–0.75) are presented. The quadrupole splittings decrease significantly in the Fe–Co and Fe–Ni systems. These changes are explained in terms of changes in site symmetry resulting in a change of orbital occupancy from d_xy to d_xz, d_yz. The changes in site symmetry are caused by changes in Fe–OH₂ bonding in the lattices ‘ squeezing ’ the Fe^II centres. The Fe–Mn system also gives results which appear to be directly related to volume change, but no evidence is found for pressure effects. The temperature dependence of the quadrupole splitting in the Fe–Mn system is discussed. It is mainly due to the Boltzmann population of the d⁶ manifolds.