Linear augmented-Slater-type-orbital method for electronic-structure calculations. IV. 5d-5d alloys

We have used local-density calculations to study a series of transition-metal compounds which are isoelectronic with rhenium: WOs, TaIr, and HfPt. The calculations were carried out for two different crystal structures, CsCl and CuAuI. We find that the heats of formation are in reasonable accord with experiment and increase with the difference in atomic number. We also find a crossover in crystal structure from CuAuI for OsW and TaIr to CsCl for HfPt, which is consistent with experiment. Charge transfer in the series was investigated by Mulliken populations and by Wigner-Seitz sphere counts. These were compared with the shifts in contact density and core-level binding energy. We find that the change in contact density is consistent with electronegativity arguments and involves both changes in s count and d (or at least non-s) screening contributions. The changes in (initial-state) core-level binding energy do not follow the same trend–in fact, for two of the compounds, the change in binding energy relative to the Fermi energy has the same sign for the two constituents.