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 PtQ(2) (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 PtQ(2) is considerably small compared with the value expected from the consideration of closely packed Q atoms (i.e., similar to 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 PtQ(2) is gradually diminished. (C) 2003 Elsevier Science (USA). All rights reserved.