On the Bindings in VOm Phases

The phenomenological plural correlations model permits to attribute to the intermediate phases of the mixture VO_M bonding types (bindings) which indicate a low energy of the empirically found structures. In the phases various electron subsystems exist which contain lattice-like spatial correlations, and when the corresponding cells are in energetically low commensurabilities (in harmonies) to the crystal and to one another then the phase becomes stable. A fundamental assumption of a binding analysis is the electron count being here V^1,4,8O^0,6,2. As a consequence the phases V₈O, V₁₆O₃, and V₇O₄ consist of a tetra-gonally deformed V(B1) partial structure with interstices partly filled by O atoms. The composition of a phase determines the electron concentrations in the subsystems, and these influence the harmony of the correlations in the binding (BF_U2 for V₁₆O₃, e.g.). In VO, V₁₃O₁₆, V₂O₃, and V₃O₅ an essentially complete close packed partial structure of O accepts V into its octahedral interstices. Once more harmonies of electron correlations determine favourable bindings (FF'2 for VO e.g.). The Magnéli phases V₄O₇ up to V₈O₁₅ being shear homeotypes of VO₂ · h may be considered as homeodesmic to TiO₂ · r, which is stabilized by a CF_U2 binding. From the binding it may be concluded how much Hund insertion is present in a phase. Hund insertion is for instance responsible for the transformation VO₂ · h → r. The phases V₆O₁₃, V₄O₉ and V₃O₇ are homeotypic to V₂O₅. This last phase permits presumably a UH_T3 binding. The results of the binding analysis of VO_M shed some new light on the interpretation of properties of the VO_M phases.