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Title: Rhombohedral Distortion of the Cubic MgCu 2-Type Structure in Ca 2Pt 3Ga and Ca 2Pd 3Ga

Two new fully ordered ternary Laves phase compounds, Ca 2Pt 3Ga and Ca 2Pd 3Ga, have been synthesized and characterized by powder and single-crystal X-ray diffraction along with electronic structure calculations. Ca 2Pd 3Ga was synthesized as a pure phase whereas Ca 2Pt 3Ga was found as a diphasic product with Ca 2Pt 2Ga. Electronic structure calculations were performed to try and understand why CaPt 2 and CaPd 2, which crystalize in the cubic MgCu 2-type Laves phase structure, distort to the ordered rhombohedral variant, first observed in the magneto-restricted TbFe 2 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 CaPd 2 and CaPt 2 (2x) to 37e -/f.u. in Ca 2Pd 3Ga and Ca 2Pt 3Ga, 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 MgCu 2-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.
Authors:
 [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Chemistry
Publication Date:
Report Number(s):
IS-J-9696
Journal ID: ISSN 2073-4352; PII: cryst8050186
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Crystals
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Journal ID: ISSN 2073-4352
Publisher:
MDPI
Research Org:
Ames Lab. and Iowa State Univ., Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; coloring problem; band structure; structure optimizations; polar intermetallics; ternary Laves phases; electronic structure; X-ray diffraction; total energy
OSTI Identifier:
1459541