Germanium monoselenide

{{redirect|GeSe||Gese (disambiguation)}}

{{chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 442207173

| ImageFile = Crystal structure of orthorhombic SnSe and GeSe.png

| ImageFile2 = GeSeskylab.jpg

| IUPACName = Germanium selenide

| OtherNames = germanium(II) selenide

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 12065-10-0

| ChemSpiderID = 21170394

| PubChem = 12049114

| StdInChI=1S/GeSe/c1-2

| StdInChIKey = RXQPCQXEUZLFTE-UHFFFAOYSA-N

| SMILES = [Ge]=[Se]

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|Section2={{Chembox Properties

| Formula = GeSe

| MolarMass = 151.57 g/mol

| Appearance = black

| Density = 5.56 g/cm³

| MeltingPtC = 667

| MeltingPt_notes = (decomposes)

| BoilingPt =

| Solubility =

| SolubleOther =

| pKa =

| RefractIndex = 2.5

| BandGap = 1.33 eV (direct) {{cite journal| title = GeSe: Optical Spectroscopy and Theoretical Study of a van der Waals Solar Absorber| author = Philip A. E. Murgatroyd, Matthew J. Smiles, Christopher N. Savory, Thomas P. Shalvey, Jack E. N. Swallow, Nicole Fleck, Craig M. Robertson, Frank Jäckel, Jonathan Alaria, Jonathan D. Major, David O. Scanlon, and Tim D. Veal| year = 2020 | journal = Chemistry of Materials| volume = 32| issue = 7| pages = 3245–3253| doi = 10.1021/acs.chemmater.0c00453| pmid = 32308255|pmc=7161679|display-authors=etal| doi-access = free}}

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|Section3={{Chembox Structure

| CrystalStruct = Orthorhombic

| SpaceGroup = Pnma

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|Section7={{Chembox Hazards

| ExternalSDS =

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|Section8={{Chembox Related

| OtherAnions = Germanium monoxide
Germanium monosulfide
Germanium telluride

| OtherCations = Tin selenide
Lead selenide

| OtherFunction =

| OtherCompounds =

| Related_ref = [http://www.webelements.com/compounds/germanium/germanium_selenide.html GeSe at webelements]

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Germanium monoselenide is a chemical compound with the formula GeSe. It exists as black crystalline powder having orthorhombic (distorted NaCl-type) crystal symmetry; at temperatures ~650 °C, it transforms into the cubic NaCl structure.{{cite journal| journal = Zeitschrift für anorganische und allgemeine Chemie| year = 1975 |volume = 411 | pages = 90–96|

title = The Thermal Expansion and High Temperature Transformation of GeSe | author = Wiedemeier H., Siemers P.A. |doi=10.1002/zaac.19754110110}} GeSe has been shown to have stereochemically active Ge 4s lone pairs that are responsible for the distorted structure and the relatively high position of the valence band maximum with respect to the vacuum level.{{cite journal| title = Ge 4s² Lone Pairs and Band Alignments in GeS and GeSe for photovoltaics| author = M. J. Smiles, J. M. Skelton, H. Shiel, L. A. H. Jones, J. E. N. Swallow, H. J. Edwards, T. J. Featherstone, P. A. E. Murgatroyd, P. K. Thakur, Tien-Lin Lee, V. R. Dhanak, and T. D. Veal| year = 2021 | journal = J. Mater. Chem. A| volume = 9| issue = 39| pages = 22440–22452| doi = 10.1039/D1TA05955F|display-authors=etal| doi-access = free| hdl = 10023/24142| hdl-access = free}}

To grow GeSe crystals, GeSe powder is vaporized at the hot end of a sealed ampule and allowed to condense at the cold end. Usual crystals are small and show signs of irregular growth, caused mainly by convective motion in the gaseous medium. However, GeSe grown under condition of zero-gravity and reduced convection aboard the Skylab are ~10 times larger than Earth-grown crystals, and are free from visual defects.{{cite web| url = https://history.nasa.gov/SP-400/ch10.htm| title = SP-400 Skylab, Our First Space Station| publisher = NASA| access-date = 2009-06-06}}{{cite journal| journal = Journal of Crystal Growth| year =1975| page = 36| author = H. Wiedemeier| doi = 10.1016/0022-0248(75)90107-4 | title = Crystal growth and transport rates of GeSe and GeTe in micro-gravity environment| volume = 31| bibcode =1975JCrGr..31...36W|display-authors=etal}}