Reinvestigation of the low-temperature form of Ag(2)Se (naumannite) based on single-crystal data.

The crystal structure of the low-temperature form of synthetic naumannite [disilver(I) selenide], Ag(2)Se, has been reinvestigated based on single-crystal data. In comparison with previous powder diffraction studies, anisotropic displacement parameters are additionally reported. The structure is composed of Se layers and two crystallographically independent Ag atoms. One Ag atom lies close to the Se layer and is surrounded by four Se atoms in a distorted tetra-hedral coordination, while the second Ag atom lies between the Se layers and exhibits a [3 + 1] coordination defined by three close Se atoms, forming a trigonal plane, and one remote Se atom.