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

Abstract

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:
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)
OSTI Identifier:
1459541
Report Number(s):
IS-J 9696
Journal ID: ISSN 2073-4352; PII: cryst8050186
Grant/Contract Number:
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Crystals
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Journal ID: ISSN 2073-4352
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
coloring problem; band structure; structure optimizations; polar intermetallics; ternary Laves phases; electronic structure; X-ray diffraction; total energy

Citation Formats

Toombs, Asa, and Miller, Gordon. Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga. United States: N. p., 2018. Web. doi:10.3390/cryst8050186.
Toombs, Asa, & Miller, Gordon. Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga. United States. doi:10.3390/cryst8050186.
Toombs, Asa, and Miller, Gordon. Thu . "Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga". United States. doi:10.3390/cryst8050186. https://www.osti.gov/servlets/purl/1459541.
@article{osti_1459541,
title = {Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga},
author = {Toombs, Asa and Miller, Gordon},
abstractNote = {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.},
doi = {10.3390/cryst8050186},
journal = {Crystals},
number = 5,
volume = 8,
place = {United States},
year = {Thu Apr 26 00:00:00 EDT 2018},
month = {Thu Apr 26 00:00:00 EDT 2018}
}

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