Germanium selenide

Germanium selenide

Names
IUPAC name Germanium selenide
Other names germanium(II) selenide
Identifiers
CAS Number	12065-10-0
ECHA InfoCard	100.031.862
PubChem	12049114
Properties
Chemical formula	GeSe
Molar mass	151.57 g/mol
Appearance	black
Density	5.56 g/cm^3
Melting point	667 °C (1,233 °F; 940 K) (decomposes)
Band gap	1.07 eV (indirect) [1] [2]
Refractive index (nD)	2.5
Structure
Crystal structure	Orthorhombic
Space group	Pnma
Related compounds[3]
Other anions	Germanium sulfide, Germanium telluride
Related	Lead selenide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Germanium selenide 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.^[4]

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.^[5][6]

References

1. L Makinistian; et al. (2007). "Ab initio calculations of the electronic and optical properties of germanium selenide". J. Phys.: C. 19: 186211. doi:10.1088/0953-8984/19/18/186211.
2. Eymard, R.; Otto, A. (1977). "Optical and electron-energy-loss spectroscopy of GeS, GeSe, SnS, and SnSe single crystals". Physical Review B. 16 (4): 1616–1623. doi:10.1103/PhysRevB.16.1616. ISSN 0556-2805.
3. GeSe at webelements
4. Wiedemeier H., Siemers P.A. (1975). "The Thermal Expansion and High Temperature Transformation of GeSe". Zeitschrift für anorganische und allgemeine Chemie. 411: 90–96. doi:10.1002/zaac.19754110110.
5. "SP-400 Skylab, Our First Space Station". NASA. Retrieved 2009-06-06.
6. H. Wiedemeier; et al. (1975). "Crystal growth and transport rates of GeSe and GeTe in micro-gravity environment". Journal of Crystal Growth. 31: 36. doi:10.1016/0022-0248(75)90107-4.