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| VOLUME 98 (2013) | ISSUE 9 | PAGE 608 |
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High-pressure polymorphism of As2S3 and new AsS2 modification with layered structure
N. B. Bolotina+, V. V. Brazhkin, T. I. Dyuzheva, Y. Katayama*, L. F. Kulikova, L. V. Lityagina, N. A. Nikolaev
+Shubnikov Institute of Crystallography of the RAS, 119333 Moscow, Russia Vereshchagin Institute for High Pressure Physics of the RAS, 142190 Troitsk, Russia *Japan Atomic Energy Agency, 1-1-1 Kuoto, Sayo-cho, Sayo-gun, 679-5143 Hyogo, Japan
Abstract
At normal pressure, the As2S3 compound is the most stable equilibrium modification with unique layered structure. The possibility of high-pressure polymorphism of this substance remains questionable. Our research showed that the As2S3 substance was metastable under pressures P> 6 GPa decomposing into two high-pressure phases: As2S3→AsS2+AsS. New AsS2 phase can be conserved in the single crystalline form in metastable state at room pressure up to its melting temperature (470 K). This modification has the layered structure with P1211 monoclinic symmetry group; the unit-cell values are a = 7.916(2) Å, b = 9.937(2) Å, c = 7.118(1) Å, β = 106.41° (Z=8, density 3.44 g/cm3). Along with the recently studied AsS high-pressure modification, the new AsS2 phase suggests that high pressure polymorphism is a very powerful tool to create new layered-structure phases with "wrong" stoichiometry. |