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AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

TitleAAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition
Publication TypeJournal Article
Year of Publication2018
AuthorsPham, J, Miller, GJ
JournalInorganic Chemistry
Volume57
Pagination4039-4049
Date Published04
Type of ArticleArticle
ISBN Number0020-1669
Accession NumberWOS:000429283200059
Keywordsal, au system, chemistry, crystal-structure, diagram, gold, Intermetallic compounds, metals, reme phases, scandium, ternary phases
Abstract

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co2Si-type to distorted hexagonal Fe2P-type and then Ni2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. The electronic origin of the Mg2Ga-type crystal structure of ScAuAl, refined as a distorted Fe2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.

DOI10.1021/acs.inorgchem.8b00214
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