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Title: An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System

Abstract

A new icosahedral quasicrystalline phase, CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.40(6); CaAu4.4Al1.6, aQC = 5.383(4) Å, and Pm35], and its lowest-order 1/0 cubic crystalline approximant phase, CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1); a = 9.0766(5)–9.1261(8) Å, Pa3(No. 205), and Pearson symbol cP40], have been discovered in the Ca-poor region of the Ca–Au–Al system. In the crystalline approximant, eight [Au3–xAl1+x] tetrahedra fill the unit cell, and each tetrahedron is surrounded by four Ca atoms, thus forming a three-dimensional network of {Ca4/4[Au3–xAl1+x]} tetrahedral stars. Here, a computational study of Au and Al site preferences concurs with the experimental results, which indicate a preference for near-neighbor Au–Al interactions over Au–Au and Al–Al interactions. Analysis of the electronic density of states and the associated crystal orbital Hamilton population curves was used to rationalize the descriptions of CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.46(6)] and CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1)] as polar intermetallic species, whereby Ca atoms engage in polar covalent bonding with the electronegative, electron-deficient [Au3–xAl1+x] tetrahedral clusters and the observed phase width of the crystalline approximant.

Authors:
 [1];  [2];  [2];  [1]
  1. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)
  2. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; National Science Foundation (NSF)
OSTI Identifier:
1347806
Grant/Contract Number:  
AC02-06CH11357; AC02-07CH11358; DMR 10-05765
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 55; Journal Issue: 20; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; group theory; electronic structure; gold; intermetallics; physical and chemical processes

Citation Formats

Pham, Joyce, Kreyssig, Andreas, Goldman, Alan I., and Miller, Gordon J. An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System. United States: N. p., 2016. Web. doi:10.1021/acs.inorgchem.6b01636.
Pham, Joyce, Kreyssig, Andreas, Goldman, Alan I., & Miller, Gordon J. An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System. United States. https://doi.org/10.1021/acs.inorgchem.6b01636
Pham, Joyce, Kreyssig, Andreas, Goldman, Alan I., and Miller, Gordon J. 2016. "An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System". United States. https://doi.org/10.1021/acs.inorgchem.6b01636. https://www.osti.gov/servlets/purl/1347806.
@article{osti_1347806,
title = {An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System},
author = {Pham, Joyce and Kreyssig, Andreas and Goldman, Alan I. and Miller, Gordon J.},
abstractNote = {A new icosahedral quasicrystalline phase, CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.40(6); CaAu4.4Al1.6, aQC = 5.383(4) Å, and Pm35], and its lowest-order 1/0 cubic crystalline approximant phase, CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1); a = 9.0766(5)–9.1261(8) Å, Pa3(No. 205), and Pearson symbol cP40], have been discovered in the Ca-poor region of the Ca–Au–Al system. In the crystalline approximant, eight [Au3–xAl1+x] tetrahedra fill the unit cell, and each tetrahedron is surrounded by four Ca atoms, thus forming a three-dimensional network of {Ca4/4[Au3–xAl1+x]} tetrahedral stars. Here, a computational study of Au and Al site preferences concurs with the experimental results, which indicate a preference for near-neighbor Au–Al interactions over Au–Au and Al–Al interactions. Analysis of the electronic density of states and the associated crystal orbital Hamilton population curves was used to rationalize the descriptions of CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.46(6)] and CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1)] as polar intermetallic species, whereby Ca atoms engage in polar covalent bonding with the electronegative, electron-deficient [Au3–xAl1+x] tetrahedral clusters and the observed phase width of the crystalline approximant.},
doi = {10.1021/acs.inorgchem.6b01636},
url = {https://www.osti.gov/biblio/1347806}, journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 20,
volume = 55,
place = {United States},
year = {Wed Sep 28 00:00:00 EDT 2016},
month = {Wed Sep 28 00:00:00 EDT 2016}
}

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