Octahedral hole, metallic field

I shall take the simple view that most metal oxide structures are derivatives of a closest packed 02 lattice with the metal ions occupying tetrahedral or octahedral holes in a manner which is principally determined by size, charge (and hence stoichiometry) and d configuration (Jj). The presence of d electrons can lead to pronounced crystal field effects or metal-metal bonding. The latter can lead to clustering of metal atoms within the lattice with large distortions from idealized (ionic) geometries. 

Figure 3. Representation of the metallic field in an octahedral hole (A) void and (B) filled...

Some ternary and mixed-valency oxides have the spinel structure where metal ions occupy a proportion of tetrahedral and octahedral holes in a cubic close-packed lattice (see Topic G5). Examples include M304 with M=Mn, Fe, Co. The distribution of M2+ and M3+ ions between the tetrahedral and octahedral sites shows the influence of ligand field stabilization energies (see Topic H2). In Fe304, Fe2+ (3d6) has an octahedral preference whereas Fe3+ (3d5) has none, and this... 

We discussed above the analysis of core-level spectra from cuprates which contain only a single hole in the d-band per Cu ion. This makes an irrelevant parameter within an impurity model. However, analysis can also be carried out for systems where [7dd plays a significant role. This is illustrated by the analysis of the core-level spectrum of LaCoOj carried out within the impurity model (Chainani et al, 1992). This oxide is modelled by the (CoOg) cluster with the transition-metal ion being formally in the 3 + oxidation state and in an octahedral crystal field. One has to therefore take into account interactions between various configurations such as d >, d Z, > >. ... 

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