Telluride crystal structure

Molecular and crystal structures of the macroheterocycle 102 were studied by X-ray [96JCS(D)1203]. As for bis-imines of di(o-formylphenyl) telluride 106, [89MI1 91JOM(402)331] only one of two potentially possible intramolecular coordination N Te bonds exists in a molecule of the macrocycle 102, which, in... 

The fourth and final crystal structure type common in binary semiconductors is the rock salt structure, named after NaCl but occurring in many divalent metal oxides, sulfides, selenides, and tellurides. It consists of two atom types forming separate face-centered cubic lattices. The trend from WZ or ZB structures to the rock salt structure takes place as covalent bonds become increasingly ionic [24]. 

It is quite difficult to explain this difference in the behavior of similar compounds. The factors which can account for these differences in the evaporation mechanisms can be reduced to two. First, we have the presence of intermediate phases which are less rich in Se or Te, and which are not observed in the bismuth—sulfur system [20-22]. The presence of intermediate phases, even though they decompose peritectically below the meltii points of Bi2X3, should stabilize bismuth selenide and telluride against thermal dissociation. Secondly, bismuth selenide and telluride have one type of crystal structure and bismuth sulfide has a different structure. The telluride and selenide have layered lattices and the sulfide has a chain lattice but with some sulfur atoms outside the chains [23, 24]. It is natural to assume that such sulfur atoms are bound less strongly to the lattice and this accounts for the ease of thermal dissociation in bismuth sulfide. 

Men kov et al. (1959, 1961) synthesised two scandium tellurides and determined their crystal structures. The data of Men kov et al. (1959) about the cubic y -AhOs-type structure for the compound Sc2Te3 had not been confirmed by a single-crystal structure investigation of that phase performed by White and Dismukes (1965) (see table 12). The latter authors obtained also a specimen of Sc2.3Te3 composition isotypic with Sc2Te3 with the lattice parameters a=4.113, c=4.051 A. This result seems to indicate the occurrence... 

The lattice is rhombohedral R3tn. The scandium atoms occupy the octahedral sites situated between each layer of tellurium. One layer of cations in two is completely full, while the other has only 5 of its sites occupied in a disordered way. A nonstoichiometric Sc7/3Tej telluride is described in the same crystal structure with a partial filling of the vacant sites (White et al., 1965b). 

The volume III/14b on structure data of sulfides, selenides and tellurides is the first part of a series of volumes which are conceived as supplement and extension to Landolt-Bomstein, New Series, Vol. III/6, Structure Data of Elements and Intermetallic Phases . They are a compilation of structure data of substances whose crystal structure was examined by means of diffraction methods (X-ray, neutron or electron diffraction) by which at least their elementary cell has been determined, or which are isotypic with substances of well known crystal structure. 

The prediction may be made that the still unstudied crystal magnesium telluride, with the radius ratio 0.29, has the sphalerite or wurzite structure rather than the sodium chloride structure. 

It is also shown that theoretically a binary compound should have the sphalerite or wurzite structure instead of the sodium chloride structure if the radius ratio is less than 0.33. The oxide, sulfide, selenide and telluride of beryllium conform to this requirement, and are to be considered as ionic crystals. It is found, however, that such tetrahedral crystals are particularly apt to show deformation, and it is suggested that this is a tendency of the anion to share an electron pair with each cation. 

The telluride halides crystallize in monoclinic lattices, but only In-TeBr and InTel are isotypic 162). InTeCl forms a layer type of structure, as do InSCl and its analogs, but, owing to the size of the Te atom and the enhanced covalency of the In-Te bond, only a coordination number of 4 for indium is realized. The structure is built up of strongly distorted, InTesraCli/j tetrahedra that share the corners and edges occupied by Te atoms. The Cl atoms are coordinated to one tetrahedron each, and do not take part in the layer formation 324, 325). 

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