Germanium monoselenide is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

GeSe. It exists as black crystalline powder having

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

(distorted

NaCl Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

-type) crystal symmetry; at temperatures ~650 °C, it transforms into the cubic NaCl structure. 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. 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 Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations in ...

are ~10 times larger than Earth-grown crystals, and are free from visual defects.

References

{{Selenides Germanium(II) compounds Selenides