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Strong positive and negative deviations from Vegard's rule: X‐ray powder investigations of the three quasi‐binary phase systems BiS X 1 − x Y x ( X , Y = Cl, Br, I)
Author(s) -
Schultz Peter,
Keller Egbert
Publication year - 2014
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/s2052520614000766
Subject(s) - x ray crystallography , lattice constant , crystallography , lattice (music) , binary number , diffraction , ion , asymmetry , solid solution , powder diffraction , phase diagram , phase (matter) , solubility , polyhedron , chemistry , materials science , physics , mathematics , combinatorics , arithmetic , organic chemistry , quantum mechanics , acoustics , optics
Three quasi‐binary phase systems, BiS X 1 − x Y x ( X , Y = Cl, Br, I; 0 < x < 1), have been investigated by X‐ray powder diffraction. All three systems show unlimited solubility. For BiSCl 1 − x Br x and BiSCl 1 − x I x , strong positive and negative deviations from Vegard's rule are observed with respect to the lattice parameters a and c . They are qualitatively explained by the asymmetry of the X coordination polyhedron and by anion–anion repulsions. For x < 0.32 [ x > 0.32] the BiSCl 1 − x I x system mimics the behaviour of the BiSCl 1 − y Br y [BiSBr 1 − y I y ] system (0 < y < 1).