Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga
Two new fully ordered ternary Laves phase compounds, Ca2Pt3Ga and Ca2Pd3Ga, have been synthesized and characterized by powder and single-crystal X-ray diffraction along with electronic structure calculations. Ca2Pd3Ga was synthesized as a pure phase whereas Ca2Pt3Ga was found as a diphasic product with Ca2Pt2Ga. Electronic structure calculations were performed to try and understand why CaPt2 and CaPd2, which crystalize in the cubic MgCu2-type Laves phase structure, distort to the ordered rhombohedral variant, first observed in the magneto-restricted TbFe2 compound, with the substitution of twenty-five percent of the Pt/Pd with Ga. Electronic stability was investigated by changing the valence electron count from 22e−/f.u. in CaPd2 and CaPt2 (2x) to 37e−/f.u. in Ca2Pd3Ga and Ca2Pt3Ga, which causes the Fermi level to shift to a more energetically favorable location in the DOS. The coloring problem was studied by placing a single Ga atom in each of four tetrahedra of the cubic unit cell of the MgCu2-type structure, with nine symmetrically inequivalent models being investigated. Non-optimized and optimized total energy analyses of structural characteristics, along with electronic properties, will be discussed.
- Research Organization:
- Ames Lab. and Iowa State Univ., Ames, IA (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- AC02-07CH11358
- OSTI ID:
- 2371733
- Report Number(s):
- IS-J--9696; PII: cryst8050186
- Journal Information:
- Crystals, Journal Name: Crystals Journal Issue: 5 Vol. 8; ISSN CRYSBC; ISSN 2073-4352
- Publisher:
- MDPI AGCopyright Statement
- Country of Publication:
- Germany
- Language:
- English
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