Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga

Toombs, Asa; Miller, Gordon

doi:10.3390/cryst8050186

Title: Rhombohedral Distortion of the Cubic MgCu₂-Type Structure in Ca₂Pt₃Ga and Ca₂Pd₃Ga

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.

Authors:

Toombs, Asa ^[1]; Miller, Gordon ^[1]

Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Chemistry

Publication Date:: Thu Apr 26 00:00:00 EDT 2018

Research Org.:: Ames Lab. and Iowa State Univ., Ames, IA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1459541

Report Number(s):: IS-J-9696
Journal ID: ISSN 2073-4352; PII: cryst8050186

Grant/Contract Number:: AC02-07CH11358

Resource Type:: 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:: 36 MATERIALS SCIENCE; 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.

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                    Toombs, Asa, & Miller, Gordon. Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga.  United States.  https://doi.org/10.3390/cryst8050186

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                    Toombs, Asa, and Miller, Gordon. Thu .  
"Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga".  United States.  https://doi.org/10.3390/cryst8050186.  https://www.osti.gov/servlets/purl/1459541.

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@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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Works referencing / citing this record:

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Title: Rhombohedral Distortion of the Cubic MgCu2-Type Structure in Ca2Pt3Ga and Ca2Pd3Ga

Abstract

Citation Formats

The Influence of the Valence Electron Concentration on the Structural Variation of the Laves Phases MgNi 2- x Ge x : The Influence of the Valence Electron Concentration on the Structural Variation of the Laves Phases MgNi journal, August 2017

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β-Mn-Type Co 8+ x Zn 12– x as a Defect Cubic Laves Phase: Site Preferences, Magnetism, and Electronic Structure journal, July 2013

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Geometrical and electronic links among the structures of MX2 solids: structural enumeration and electronic stability of pyritelike systems journal, March 1982

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Title: Rhombohedral Distortion of the Cubic MgCu₂-Type Structure in Ca₂Pt₃Ga and Ca₂Pd₃Ga

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Y2Rh3Ge, a rhombohedral substitution variant of the MgCu2 type
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