Keywords

binary alloys, density calculations, ordering temperatures, phase separations

Abstract

The binary alloys of Rh, Pd, Ir, and Pt are important because of their high catalytic potential. We report in this paper that the Rh1-xIrx and Rh1-xPtx systems, long thought to phase separate at low temperatures, actually exhibit miscibility over the entire concentration and temperature range. We find low critical ordering temperatures, indicating that long-range order is unlikely to be observed experimentally. These results are compared with previous theoretical predications for the other binary alloys of Rh, Pd, Ir, and Pt and with calculations performed here on the Pt1-xIrx and Pd1-xIrx systems. We discuss these results and investigate the mechanisms governing ordering vs. phase separating behavior in all six binaries of the Rh-Pd-Ir-Pt quartet. In particular, we examine why, given the chemical similarity of all members of the quartet, three of their binaries (PdIr, PtIr, and RhPd) phase separate while the remaining three (RhIr, RhPt, and PdPt) order.

Original Publication Citation

Brian Kolb, Stefan Mueller, David Botts and Gus L. W. Hart "Ordering tendencies in the binary alloys of Rh, Pd, Ir, and Pt,"Phys. Rev. B 74 14426 (3 Oct. 26). The original article may be found here: http://prb.aps.org/abstract/PRB/v74/i14/e14426