Trends in the structure and bonding in the layered platinum dioxide and dichalcogenides PtQ2 (Q=O, S, Se, Te)

The structure and bonding of the layered platinum dioxide and dichalcogenides PtQ₂ (Q=O, S, Se, Te) were analyzed on the basis of electronic band structure calculations using the full potential linearized augmented plane wave method. We examined why the c/a ratio in PtQ₂ is considerably small compared with the value expected from the consideration of closely packed Q atoms (i.e., ∼1.40 vs. 1.67), and identified the electronic factor that causes the semiconducting properties in PtO₂ and PtS₂, the semimetallic property in PtSe₂, and the metallic property in PtTe₂. To a first approximation, the oxidation states of oxygen and platinum in PtO₂ can be regarded as -2 and +4, respectively, but this picture is not applicable to PtTe₂. As the ligand Q is changed from O to S to Se to Te, the energy gap between the Pt 5d and the ligand p levels gradually decreases, so that the ionic character of the Pt-Q bonding in PtQ₂ is gradually diminished.