Structure of Two Modifications of Dysprosium Sesquisulfide, Dy2S3.

Dy2S3 (A), U2S3 type structure, M(r) = 421.18, orthorhombic, Pnma, a = 10.609 (1), b = 3.864 (1), c = 10.429 (1) angstrom, V = 427.5 (1) angstrom 3, Z = 4, D(x) = 6.543 g cm-3, lambda(Mo K-alphaBAR) = 0.71073 angstrom, mu = 362.2 cm-1, F(000) = 720, T = 298 K, R(F) = 0.023 for 947 observed reflections with I > 2.5-sigma(I). All atoms at 4(c). Two types of Dy. Dy(1) is coordinated by seven S atoms at a short distance approximately in a monocapped trigonal prism, Dy(1)-S = 2.818-2.850 angstrom (CN = 7); S capped at a second face of the trigonal prism is at Dy(1)-S = 3.310 angstrom. Dy(2) (CN = 7) is coordinated by four S atoms approximately quadratically and by three S atoms triangularly in the plane through Dy(2) parallel to (010); Dy(2)-S = 2.739-2.792 angstrom. Dy2S3 (B), alpha-Gd2S3 type structure, M(r) = 421.18, orthorhombic, Pnma, a = 7.284 (1), b = 3.881 (1), c = 15.143 (1) angstrom, V = 428.1 (1) angstrom 3, Z = 4, D(x) = 6.535 g cm-3, lambda(Mo K-alphaBAR) = 0.71073 angstrom, mu = 361.7 cm-1, F(000) = 720, T = 298 K, R(F) = 0.032 for 799 observed reflections with I greater-than-or-equal-to 2.5-sigma(I). All atoms at 4(c). Two types of Dy. Dy(1) (CN = 8) is coordinated by S approximately in a bicapped trigonal prism; Dy(1)-S = 2.732-3.057 angstrom. Dy(2) (CN = 7) is coordinated as Dy(2) in the U2S3 type structure; Dy(2)-S = 2.719-2.886 angstrom.