Chromium lattice parameter

The oxide systems deriving from chromium(III) are numerous. Chromium(III) oxide, Cr203, is the final product of the calcination of many chromium(III) complexes. Chromium(III) oxide has the A1203 structure (Ds) with hexagonal lattice parameters a = 4.95, c = 13.66A and c/a = 2.761.712... 

A pattern is made of a cubic substance with unhltered chromium radiation. The observed sin 0 values and intensities are 0.265(m), 0.321(vs), 0.528(w), 0.638(s), 0.793(s), and 0.958(vs). Index these lines and state which are due to Ka and which to Kfi radiation. Determine the Bravais lattice and lattice parameter. Identify the substance by reference to Appendix 5. 

Several new isocyanide complexes of chromium(m) have been prepared by the electrochemical reduction of heavy-metal adducts of chromium(iii) aquocyano-complexes, and characterized by their visible spectra. The chromium 2p- and 3s-orbital ionization potentials in K3[Cr(NCS)6] have been reported, and the lattice parameters for this anion in the salt with diaquotris-(nicotinic acid)holmium(iii) determined. " The absorption spectra of the... 

The reaction was found to be catalysed by the presence of chromium. In a separate investigation, the concentration dependence of the lattice parameters of this monocarbide, together with those of TiC, HfC, VC, NbC, and TaC, has been investigated. It has been shown that the significant factor affecting the parameters is whether the equilibrium M— C distance is associated with a lattice parameter greater or less than that produced by a non-screened M—M interaction. An electron diffraction study of one of these non-stoicheiometric carbides, VCi jj, which is cubic, and the hexagonal has also been completed. 

Phase equilibria for the isothermal section at 900°C of compound compositions in the ternary gadolinium-chromium-carbon system are shown in fig. 28 (Jeitschko and Behrens 1986). Only one ternary carbide, Gd2Cr2C3, exists in this system and it was found to be isotypic with HojCrjCj. The variation of the lattice parameters of samples with different compositions indicates that the homogeneity range of Gd CrTC, seems to be small. 

Hydrides can have different lattice parameters or belong to a different crystallographic system. Thus, in the case of chromium, the change of hexagonal lattice to body-centered cubic (twisting of lattice positions), which causes tensile stress, is found to be accompanied by hydrogen evolution. 

Lanthanum ions introduced into alumina structure, decrease the solubility of copper and chromium ions, thus, providing the decrease of the mineralizing effect. Copper and chromium ions not involved in the support structure, yield an extra quantity of copper chromite, which enriches coirespondingly the solid solution of CUAI2O4 and CuCr204 spinels, providing the change of the lattice parameter. 

Chromium was a metal widely used as a paramagnetic agent for doping Ti02 and other oxide lattices [220, 221, 250-266]. The electronic configurations of chromium centers are 3d3 (Cr3+, S = 3/2) and 3d1 (Cr5+, S = 1/2). Spin-Hamiltonian parameters are... 

The crystal field optical transitions of Cr + in an octahedral site are shown in Fig. 26. The splitting of the upper energy levels by the weak trigonal distortion ( 350 cm ) (67,168-170) of the octahedron cannot be resolved in powder samples of chromia-alumina. The optical reflectance spectra shown in Fig. 27 show a gradual shift of the absorption maxima near 17,000 and 23,000 cm (15,39,171) due to the lattice expansion that results when chromia is added to an alumina lattice. The optical spectra conform to the Tanabe and Sugano (168,172-174) theoretical calculations. The Racah parameter varied with the chromium content (15,171), Variable temperature (169,175) and variable pressure (176,177) optical spectra have been obtained for ruby samples. 

When Rietveld analysis is used to amend the structure of chromium-doped iron oxide samples, the structural parameters of pure 7-Fe203 is used as initial parameters. 7-F6203 has a spinel structure of Fe304 with iron ions defect, and Fc304 has the space group Fd-3m, lattice constants a = 0.8333nm, Z = 8. The parameters of atomic coordinates are listed in Table 7.16. 

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