| Résumé | It is shown here that crystallographic descriptions of hypothetical AB63, AB107, AB127, AB215 and especially AB255 stoichiometric compounds with cell edge, respectively 4, 3, 4, 6 and four times the (A,B) fcc subcell edge stick out as convenient models for ab initio studies of cell data versus composition for ccp solid-solution alloys. TheirWyckoff positions can be combined to generate most binary alloy compositions from 0% to 100% in multiples of 1/64, 1/108, 1/128, 1/216 and 1/256 while retaining the same periodicity and, respectively the same Fm¯3m, Pm¯3m, Im¯3m, Fm¯3m and Pm¯3m space group symmetry. As an application, we model cell data for three cubic solid-solution alloys of Pt. (Pt,Ir) and (Pt,Ru) remain close to Vegard’s law predictions with a slight convexity or concavity in the plot. That curvature is explainable by the magnitude and sign of the alloying energy. Modeling of (Pt,Re) between 0% and 45% Re in 50 steps of RenPt108−n stoichiometric compounds follows approximately non-Vegard experimental data but with large, unexplained spread. |
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