TY - JOUR
T1 - 2/1 and 1/1 cubic approximants in the ternary R-Cd-Mg (R = Y, Er) systems
AU - Yamada, Tsunetomo
AU - Fujita, Nobuhisa
AU - Labib, Farid
N1 - Funding Information:
Funding for this research was provided by: Japan Society for the Promotion of Science (grant Nos. JP18K04677, JP18K13987, JP19H05818 and JP19H05819).
Publisher Copyright:
© 2021 International Union of Crystallography. All rights reserved.
PY - 2021/8/1
Y1 - 2021/8/1
N2 - The atomic structures of three cubic approximants (cAPs), Y12.7Cd61.8Mg25.5 [2/1 cAP with space group Pa 3, a = 25.0654(1)Å] and Er12.5Cd72.0Mg15.5 [2/1 cAP with Pa 3, a = 24.9658(1)Å], and Y14.5Cd66.1Mg19.4 [1/1 cAP with Im 3, a = 15.4577(1)Å], were investigated using X-ray structure analysis. The two 2/1 cAPs were found to be isostructural to the binary 2/1 cAP, YbCd5.8, which is composed of two building units, namely Tsai-type rhombic triacontahedron (RTH) cluster and double-Friauf polyhedron (DFP). The 1/1 cAP, in contrast, was found to be isostructural to the binary 1/1 cAP, YbCd6, which is composed solely of the RTH cluster. The refined structure models of the three cAPs exhibit substitutional disorders due to the Mg content that enters into Cd sites of the parent binary cAPs. In addition, in the 2/1 cAPs, the Y3(Er3) site on the third icosahedron shell of the RTH cluster and two positions inside DFP, Y5(Er5) sites, are partially mixed with Mg. Moreover, characteristic positional disorders owing to orientational disorder in the first shell of the RTH cluster is observed in all the three cAPs. A close relationship between the occupational disorder of the Y3(Er3) and Y5(Er5) sites in 2/1 cAPs and the elemental distribution in their first coordination shells is revealed.
AB - The atomic structures of three cubic approximants (cAPs), Y12.7Cd61.8Mg25.5 [2/1 cAP with space group Pa 3, a = 25.0654(1)Å] and Er12.5Cd72.0Mg15.5 [2/1 cAP with Pa 3, a = 24.9658(1)Å], and Y14.5Cd66.1Mg19.4 [1/1 cAP with Im 3, a = 15.4577(1)Å], were investigated using X-ray structure analysis. The two 2/1 cAPs were found to be isostructural to the binary 2/1 cAP, YbCd5.8, which is composed of two building units, namely Tsai-type rhombic triacontahedron (RTH) cluster and double-Friauf polyhedron (DFP). The 1/1 cAP, in contrast, was found to be isostructural to the binary 1/1 cAP, YbCd6, which is composed solely of the RTH cluster. The refined structure models of the three cAPs exhibit substitutional disorders due to the Mg content that enters into Cd sites of the parent binary cAPs. In addition, in the 2/1 cAPs, the Y3(Er3) site on the third icosahedron shell of the RTH cluster and two positions inside DFP, Y5(Er5) sites, are partially mixed with Mg. Moreover, characteristic positional disorders owing to orientational disorder in the first shell of the RTH cluster is observed in all the three cAPs. A close relationship between the occupational disorder of the Y3(Er3) and Y5(Er5) sites in 2/1 cAPs and the elemental distribution in their first coordination shells is revealed.
KW - approximants
KW - quasicrystals
KW - structure analysis
KW - X-ray diffraction
UR - http://www.scopus.com/inward/record.url?scp=85112087382&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85112087382&partnerID=8YFLogxK
U2 - 10.1107/S2052520621006715
DO - 10.1107/S2052520621006715
M3 - Article
AN - SCOPUS:85112087382
VL - 77
SP - 638
EP - 648
JO - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
JF - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
SN - 2052-5206
ER -