Incommensurately modulated lanthanide coinage-metal diarsenides. II. GdCuAs2, GdAu(1-delta)As2 and TbAu(1-delta)As2--new distortion variants of the HfCuSi2 type with irregularly stacked zigzag chains of arsenic atoms.
GdCuAs2, GdAu(1-delta)As2 and TbAu(1-delta)As2 crystallize as incommensurately modulated variants of the HfCuSi2 type. Structure models have been developed in the monoclinic superspace group P12(1)/m1(alpha0gamma)00 (No. 11.1). The components of the modulation wavevectors q = alphaa* + 0b* + gammac* are alpha = 0.04 (1) and gamma = 0.48 (1) for GdCuAs2, alpha = 0.03 (1) and gamma = 0.48 (1) for GdAu(1-delta)As2 and alpha = 0.02 (1) and gamma = 0.46 (1) for TbAu(1-delta)As2. The predominant effect of the positional modulation is the distortion of a square net of arsenic atoms, which results in planar zigzag chains. Rod groups and layer groups of the respective structure motifs are identified and discussed.
Rutzinger
D
D
Department of Chemistry and Food Chemistry, Technische Universität Dresden, D-01062 Dresden, Germany.
Bartsch
C
C
Doert
Th
T
Ruck
M
M