High pressure metallurgy: High pressure synthesis and structural analysos of new intermetallic compounds containing light nonmetallic sp-elements

• Applicant: Professor Dr. Wilfried B. Holzapfel
• Subject Area: Molecular Chemistry
• Term: from 1999 to 2002
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5191228

We propose to produce under high pressure new intermetallic phases in binary alloy systems displaying at ambient conditions only a simple mixture of the constituents. Special interest provide alloys of group IV elements (Si, Ge, Sn), which show under pressure a sequence of transformations form semiconductor/semimetal to metallic states. Phase equilibria in these alloy systems change therefore under pressure from "semiconductor/semimetal-metal" type to "metal-metal" type. By this evolution new intermetallic phases can arise, which are controlled by known 'metallic' rules like Vegard's law or the Hume-Rothery rule, which points to the fact that the phase stability of those sp-metal alloys is then largely controlled by the valence electron concentration (Hume-Rothery phases). Studies under pressure on intermetallic binary alloys involving light non-metallic group IV elements can extend and modify the known structural maps of polyvalent sp-metals and can elucidate thereby the main factors controlling structural stability like variation in atomic volume and valence electron concentration through the variation in the band structure energy. A better understanding of these factors should have a strong impact on synthesis and processing of a large variety of novel advanced materials.

• DFG Programme: Research Grants
• International Connection: Russia
• Participating Persons: Valentina Degtyareva; Professor Dr. E. G. Ponyatovskii; Professor Dr. Veniamin Shekhtman