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The most stable and dense form of selenium is gray and has a chiral hexagonal crystal lattice (space group 152 or 154 depending on the chirality) [19] consisting of helical polymeric chains, where the Se–Se distance is 237.3 pm and Se–Se–Se angle is 103.1°. The minimum distance between chains is 343.6 pm. Gray selenium is formed by mild ...
Tungsten diselenide is an inorganic compound with the formula WSe 2. [6] The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide.The tungsten atoms are covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere while each selenium is bonded to three tungsten atoms in a pyramidal geometry.
Selenium has a hexagonal polyatomic (CN 2) crystalline structure. It is a semiconductor with a band gap of 1.7 eV, and a photoconductor meaning its electrical conductivity increases a million-fold when illuminated. Selenium has a moderate ionisation energy (941.0 kJ/mol), high electron affinity (195 kJ/mol), and high electronegativity (2.55).
The high temperature phase is the hexagonal, NiAs structure (P6 3 /mmc) δ-Fe 1−x Se. Iron(II) selenide occurs naturally as the NiAs -structure mineral achavalite . More selenium rich iron selenide phases are the γ phases (γ and γˈ), assigned the Fe 3 Se 4 stoichiometry , and FeSe 2 , which occurs as the marcasite -structure natural ...
Within the titanium-selenium system, many stoichiometries have been identified. Titanium diselenide crystallizes with the CdI 2-type structure, in which the octahedral holes between alternating hexagonal closely packed layer of Se 2− layers (that is half of the total number of octahedral holes) are occupied by Ti 4+ centers.
Heating the cubic form gives hexagonal ZnSe. An alternative synthesis involves heating a mixture of zinc oxide, zinc sulfide, and selenium: 2 ZnO + ZnS + 3 Se → 3 ZnSe + SO 2. It is a wide-bandgap semiconductor of the II-VI semiconductor group (since zinc and selenium belong to the 12th and 16th groups of the periodic table, respectively).
A much thicker layer of selenium (50 to 60 μm) doped with a halogen is deposited on top of the thin metal plating. The selenium is then converted into polycrystalline gray (hexagonal) form by annealing. Cadmium selenide forms by reaction of the selenium with the tin-cadmium alloy and the CdSe-Se heterojunction is the
Chromium(II) selenide is an inorganic compound with the chemical formula CrSe. It crystalizes in a hexagonal structure with space group P6 3 /mmc. [3] It is one of many related chromium-selenium phases, including Cr 2 Se 3, as well as Cr 7 Se 8, Cr 3 Se 4, Cr 0.68 Se, and Cr 5 Se 8. [3]