CRYSTAL STRUCTURE OF BAUMHAUERITE

The crystal structure of baumhauerite Pb11,6As15,7Ag0,6S36 is redetermined. The unit cell is triclinic with a = 22.80 ± 0.01 Å, b = 8.357 ± 0.005 Å, c = 7.894 ± 0.005 Å, α = 90°3' ± 2', β = 97°16' ± 4', γ = 89°55' ± 2'. The spate group is P1. Among twelve independent Pb atoms, the eight “paired” (1, 2, 6, 7, 8, 9, 11, 12) are surronded by nine S atoms, the four “unpaired” (3, 4, 5, 10) are surrounded by seven S atoms. The As atoms are coordinated by S atoms in a trigonal pyramidal configuration. The Pb(4) is partially replaced by As. The As(5) occupies statistically two neighbouring places 5a, 56. The As(4) is partially replaced by Ag. AsS3 pyramids form chains of finite length. © 1969, Walter de Gruyter. All rights reserved.