Tungsten diselenide

Crystal structure
	__ W 4+ __ Se 2−
General
Surname	Tungsten diselenide
other names	Tungsten (IV) selenide
Ratio formula	WSe 2
Brief description	black, odorless solid
External identifiers / databases
EC number	235-078-7
ECHA InfoCard	100,031,877
PubChem	82910
ChemSpider	74810
Wikidata	Q2592220
properties
Molar mass	341.78 g · mol -1
Physical state	firmly
density	9.32 g cm −3
Melting point	from 850 ° C decomposition
solubility	almost insoluble in water
safety instructions
H and P phrases	H: 301-331-373-410
	P: 260-264-403 + 233
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tungsten diselenide (tungsten (IV) selenide) is a semiconductor compound with hexagonal symmetry and the empirical formula WSe ₂ . It has a large anisotropy of electrical properties. Crystals made from this material consist of layers of the two elements ( tungsten and selenium ) which are only held together by van der Waals forces . Within the respective layer of the connection, all valence orbitals form covalent bonds , so that there are consequently no free valence electrons on the surface . Therefore, the connection (like other compounds that have this type of chemical bond) is stable at their interfaces and relatively free of contamination , but can be split very easily along the plane of the layer.

Extraction and presentation

Tungsten diselenide can be obtained directly from the elements at around 500 ° C.

{\ displaystyle \ mathrm {W + 2 \ Se \ longrightarrow WSe_ {2}}}

use

The compound is used as a solid lubricant, as a model semiconductor for investigating the photoeffect in thin-film solar cells and as a base material for the self-organization of metal atoms on surfaces. It was also discovered that the material is one of the best known heat insulators due to its layered structure.

Individual evidence

↑ ^a ^b ^c ^d data sheet Tungsten (IV) selenide, 99.8% (metals basis) from AlfaAesar, accessed on December 7, 2019 ( PDF )(JavaScript required) .
↑ tungsten diselenide at webelements.com
^ Hermann Jehn, Gudrun Bär, Erich Best, Ernst Koch: W Tungsten Supplement Volume A 5 b Metal, Chemical Reactions with Nonmetals Nitrogen to Arsenic . Springer Science & Business Media, 2013, ISBN 978-3-662-08684-1 , p. 117 ( limited preview in Google Book search).
↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the indicated labeling it falls under the group entry selenium compounds with the exception of cadmium sulphoselenide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Thien Binh Vu, N. Garca-A, Klaus Dransfeld: Nanosources and Manipulation of Atoms Under High Fields and Temperatures: Applications . Springer Science & Business Media, 1993, ISBN 978-0-7923-2266-5 , pp. 295 ( limited preview in Google Book search).
^ Hermann Jehn, Gudrun Bär, Erich Best: W Tungsten Supplement Volume A 5 b Metal, Chemical Reactions with Nonmetals Nitrogen to Arsenic . Springer Science & Business Media, 2013, ISBN 978-3-662-08684-1 , p. 117 ( limited preview in Google Book search).
^ Klaus Lüders, Gebhard von Oppen: Classical Physics - Mechanics and Heat . Walter de Gruyter, 2012, ISBN 978-3-11-022668-3 , p. 239 ( limited preview in Google Book search).
^ Perrin Walker, William H. Tarn: CRC Handbook of Metal Etchants . CRC Press, 1990, ISBN 978-1-4398-2253-1 , pp. 1285 ( limited preview in Google Book Search).
↑ Chiritescu, C., Cahill, DG, Nguyen, N., Johnson, D., Bodapati, A., Keblinski, P., & Zschack, P .: Ultralow thermal conductivity in disordered, layered WSe2 crystals . In: Science . tape 315 (5810) , 2007, pp. 351-353 .

[Alfa-1] ta sheet Tungsten (IV) selenide, 99.8% (metals basis) from AlfaAesar, accessed on December 7, 2019 ( PDF )(JavaScript required) .

[webelements-2] tungsten diselenide at webelements.com

[Hermann_Jehn,_Gudrun_Bär,_Erich_Best,_Ernst_Koch-3] Hermann Jehn, Gudrun Bär, Erich Best, Ernst Koch: W Tungsten Supplement Volume A 5 b Metal, Chemical Reactions with Nonmetals Nitrogen to Arsenic . Springer Science & Business Media, 2013, ISBN 978-3-662-08684-1 , p. 117 ( limited preview in Google Book search).

[CLP_100.240.771-4] Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the indicated labeling it falls under the group entry selenium compounds with the exception of cadmium sulphoselenide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[Thien_Binh_Vu,_N._Garca-A,_[[Klaus_Dransfeld]]-5] Thien Binh Vu, N. Garca-A, Klaus Dransfeld: Nanosources and Manipulation of Atoms Under High Fields and Temperatures: Applications . Springer Science & Business Media, 1993, ISBN 978-0-7923-2266-5 , pp. 295 ( limited preview in Google Book search).

[Hermann_Jehn,_Gudrun_Bär,_Erich_Best-6] Hermann Jehn, Gudrun Bär, Erich Best: W Tungsten Supplement Volume A 5 b Metal, Chemical Reactions with Nonmetals Nitrogen to Arsenic . Springer Science & Business Media, 2013, ISBN 978-3-662-08684-1 , p. 117 ( limited preview in Google Book search).

[Klaus_Lüders,_Gebhard_von_Oppen-7] Klaus Lüders, Gebhard von Oppen: Classical Physics - Mechanics and Heat . Walter de Gruyter, 2012, ISBN 978-3-11-022668-3 , p. 239 ( limited preview in Google Book search).

[Perrin_Walker,_William_H._Tarn-8] Perrin Walker, William H. Tarn: CRC Handbook of Metal Etchants . CRC Press, 1990, ISBN 978-1-4398-2253-1 , pp. 1285 ( limited preview in Google Book Search).

[Cahill-9] Chiritescu, C., Cahill, DG, Nguyen, N., Johnson, D., Bodapati, A., Keblinski, P., & Zschack, P .: Ultralow thermal conductivity in disordered, layered WSe2 crystals . In: Science . tape 315 (5810) , 2007, pp. 351-353 .