Abstract
The heats of formation, ΔH, of the ordered phases of Pt-Ti are calculated using various approximations. This alloy system was chosen because of the availability of experimental data for ΔH for both high- and low-symmetry phases. The difference in the calculated heats of formation between a muffin-tin and a full-potential treatment can be substantial, as much as 0.25 eV/atom. While the total energies of the compounds and the reference elemental metals are all lowered (i.e., increased in binding), the change in ΔH depends on which energy is lowered more. For PtTi in the high-symmetry CsCl structure, ΔH is reduced, implying that the decrease of the total energy due to the full potential is larger for the elemental reference solids than for the compound. The calculated heats of formation are in accord with the experimental values and the known phase-diagram behavior, i.e., all the low-temperature phases predicted to occur as a function of composition are in fact observed.
- Received 8 October 1991
DOI:https://doi.org/10.1103/PhysRevB.45.8233
©1992 American Physical Society