1 Department of Chemistry, Iowa State University, Ames, IA 50011-3111, USA; toombsa@iastate.edu
2 Ames Laboratory, U.S. Department of Energy, Ames, IA 50011-3111, USA
* Correspondence: gmiller@iastate.edu
Received: 27 March 2018; Accepted: 24 April 2018; Published: 26 April 2018
Abstract:
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.
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1196&context=ameslab_manuscripts
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