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Distorted Te nets in the modulated crystal structures of RE Te 1.94(1) ( RE = La, Pr, Nd)
Author(s) -
Poddig Hagen,
Doert Thomas
Publication year - 2020
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520620013797
Subject(s) - tetragonal crystal system , crystallography , stacking , planar , superspace , crystal structure , diffraction , materials science , chemistry , crystal (programming language) , optics , physics , computer graphics (images) , organic chemistry , supersymmetry , computer science , mathematical physics , programming language
The two‐dimensionally incommensurately modulated crystal structures of the compounds RE Te 1.94(1) ( RE = La, Pr, Nd) were investigated by single‐crystal X‐ray diffraction. The compounds crystallize in the tetragonal superspace group P 4/ n (αβ½)00(−βα½)00 (No. 85.2.58.2) with q 1 = α a *+β b *+½ c * and q 2 = −β a *+α b *+½ c * and share a common motif of an alternating stacking of a puckered [ RE Te] layer and a planar [Te] layer. This basic structural motif is observed for all reported compounds with unusually large anisotropic displacement parameters in the planar [Te] layer. Taking the modulation into account, a distortion from this perfect square planar net is noted along with vacancies in the planar [Te] layer. The distortion leads to the formation of different discrete anions, like Te 2− , Te 2 2− and Te 3 2− , similar to previously reported structures for RE X 2–δ compounds ( RE = trivalent rare earth metal, X = S, Se, Te). The Te–Te distances in the modulated [Te] layer are found in a narrow range as compared to those in the corresponding sulfides and selenides.