Argentite-Acanthite Transformation in Silver Sulfide as a Disorder-Order Transition
An alternative model has been proposed for the phase transition from cubic argentite ß-Ag2S to monoclinic acanthite α-Ag2S in silver sulfide as a disorder–order transition. It has been shown that, as the temperature decreases below the transition temperature Ttrans, S atoms equiprobably occupying the sites of the body centered cubic (bcc) nonmetal sublattice of argentite are concentrated at four sites of the monoclinic nonmetal sublattice, whereas the other sites remain vacant. A disorder-order transition channel including three superstructure vectors of k9 and k4 stars has been determined. The distribution function of sulfur atoms in monoclinic acanthite α-Ag2S has been calculated. It has been shown that displacements of sulfur atoms distort the bcc nonmetal sublattice of argentite, forming a monoclinic lattice, where silver atoms are spaced by quite large distances and occupy their crystallographic positions with a probability of 1. The region of allowed values of the long-range order parameters η9 and η4 for the model monoclinic ordered phase α-Ag2S has been determined.
Unable to display preview. Download preview PDF.
- 1.R. C. Sharma and Y. A. Chang, Bull. Alloy Phase Diagrams 7, 263 (1986).Google Scholar
- 10.A. I. Gusev, Nonstoichiometry and Chaos, Short- and Long-Range Orders in Solids (Fizmatlit, Moscow, 2007) [in Russian].Google Scholar
- 11.A. A. Rempel and A. I. Gusev, Nonstoichiometry in Solids (Fizmatlit, Moscow, 2018) [in Russian].Google Scholar
- 13.A. G. Khachaturyan, Theory of Phase Transformations and the Structure of Solid Solutions (Nauka, Moscow, 1974) [in Russian].Google Scholar
- 14.O. V. Kovalev, Irreducible and Induced Representations and Corepresentations of Fedorov’s Groups (Nauka, Moscow, 1986) [in Russian].Google Scholar
- 15.Yu. A. Izyumov, V. E. Naish, and R. P. Ozerov, Neutron Diffraction of Magnetic Materials (Atomizdat, Moscow, 1981; Consultants Bureau, New York, 1991).Google Scholar
- 19.F. Grønvold and E. F. Westrum, J. Chem. Thermodyn. 18, 381 (1986).Google Scholar