User:Graeme Bartlett/thioarsenate

Thioarsenates are chemical compounds which contain anionic units of sulfur connected to arsenic. They can be considered as arsenates where sulfur substitutes for oxygen. Similar compounds include the selenoarsenates, thiophosphates and thioantimonates. They are in the category of chalcogenopnictates or more broadly chalcogenometallates.

Formation

Thioarsenates may be produced by heating a metal azide with arsenic and sulfur in a sealed tube.

Thioarsenates containing Se₂ units are formed by heating with selenium. Conversely, by heating, extra sulfur vapour can be lost forming a compound with less sulfur.

Properties

Most thioarsenates are semiconductors. Their resistance drops on exposure to light. Also thioarsenates are often coloured, most often red.

?????? Thioarsenate structures can include rings such as the four-membered ring: [^{—————}
_AsSAsS] or the five-membered [^{——————}
_AsSSAsS]. These can be linked into chains.

Use

Thioarsenates are primarily of research interest. ?????They are being researched for photovoltaic cells where efficiencies over 20% are possible, and for photoconductors, and non-linear optical devices.

List

name	chem	mw	crystal system	space group	unit cell Å	volume	density	comment	CAS no	references
	SrAgAsS4			Ama2	a=10.2597 b=10.1558 c=6.4730			band gap 2.31 eV; NLO