The elastic constants, phase stability, heat of formation and the Debye temperature of various
noble metal compounds in the stoichiometry A3B (where A = Pt, Ir, Rh, Ru, Pd and B = Al,
Hf, Zr, Sc) were studied using the ab initio Density Functional Theory - Projector Augmented
Wave method. A total of 24 compositions was investigated, of which 16 compounds were
predicted to be thermodynamically stable. The remaining eight compounds were found not
energetically favorable, due to positive or low heats of formation. According to the Density
of States studies, the L12 structure was predicted in 8 compounds while four compounds had
the D024 structure. Among compounds with the L12 structure, the hardest phase predicted
was L12-Ir3Hf. L12-Pd3Sc was predicted as the least hard and most ductile compound. In
compounds with the D024 structure, Pt3Zr was predicted having highest hardness and highest
melting point. In all the compounds, the strongest interaction was found between hafnium
and the noble metals and least interaction was with aluminum. The melting points from
ab initio and molecular dynamics calculations slightly over-predicted experimental values,
but showed the same trends. Both the fracture toughnesses and the melting points deduced using the Sutton-Chen potentials had similar trends to ab initio results, suggesting that the
Sutton-Chen potentials is adequate for simulating metallic phases.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/14037 |
| Date | 06 March 2014 |
| Creators | Popoola, Adewumi Isaac |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf, application/pdf |
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