Marcasite structure compounds

Table III. Cl Shifts of Some Marcasite Structure Compounds...

P-P groups in compounds with the pyrites or marcasite structures, discrete P4 rings in IrP3 etc. (C0AS3 structure), chains in PdP2, layers in CdP4. 

A number of selenium and tellurium compounds of the presently discussed metals show a quite different behavior from the Fe-S system. Iron and selenium form two compounds FeSe with a broad stoichiometry range and FeSe2 with a much narrower composition field. Below 400 the non-stoichiometric Fei xSe exists by creation of iron vacancies and can have compositions lying between FeySes and Fe3Se4. At low temperatures there exist two phases an a (PbO type) and a f) (NiAs type) phase. The crystal sUiicture of the diselenide, FeSe2, is an orthorhombic, C18 (marcasite) type. In the Fe-Te system, the defect NiAs structure is found at a composition close to FeTei.s, as about one-third of the Fe atoms are missing. At compositions around FeTe the behavior is complex, and the f)-phase has the PbO structure (like FeSe) but with additional metal atoms (i.e., FeuTe). 

Ru and Os alloys. A specimen of structure types observed in the alloys of these metals (very often as solid solution ranges) is shown in Table 5.48a. The formation of Laves-type phases, a phases and several CsCl-type phases can be underlined. Notice the formation of marcasite and pyrite type compounds with the semimetals and non-metals of the 15th and 16th groups. 

Compounds with Pyrite, Ullmannite, Marcasite and Arsenopyrite Structure... 

Marcasites and arsenopyrites are a common structural choice for MA2 compounds, where M is a late transition metal, A a group 15 or 16 element. The structure, 133, is related to the rutile one, in that one can easily perceive in the structure the octahedral coordination of the metal, and onedimensional chains of edge-sharing octahedra. The ligands are now... 

Goodenough, J. B. (1972). Energy bands in TX compounds with pyrite, marcasite and arsenopyrite structures. J. Solid State Chem. 5, 144-52. 

Among the pnictide elements, phosphorus and arsenic seem to be most likely to form mixed crystals with metals. The compounds OSP2, OsAs2 and OsAsP, for example, all have the marcasite type of structure. Mixed systans of type GaAs Pi are of great importance in semiconductor and other devices (Chapter 12.20). 

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