Cadmium crystal structure

Cadmium crystallizes in the hep system. Its electronic structure is 5s24p2 and the melting point is 594 K. The first attempt to determine Ev=o of (0001) and (1010) Cd faces by C, curves was made by Abdullin... 

The differing malleabilities of metals can be traced to their crystal structures. The crystal structure of a metal typically has slip planes, which are planes of atoms that under stress may slip or slide relative to one another. The slip planes of a ccp structure are the close-packed planes, and careful inspection of a unit cell shows that there are eight sets of slip planes in different directions. As a result, metals with cubic close-packed structures, such as copper, are malleable they can be easily bent, flattened, or pounded into shape. In contrast, a hexagonal close-packed structure has only one set of slip planes, and metals with hexagonal close packing, such as zinc or cadmium, tend to be relatively brittle. 

Inorganic pigments, 29 375-417 black pigments, 29 408-410 chemical properties of, 29 377-378 classification of, 29 402 colored pigments, 29 397-408 crystal structure of, 29 377-378 durability of, 29 382-384 environmental aspects of, 29 413-415 lead- and cadmium-containing, 29 414-415... 

Phosphate and cadmium uptake in HH. In the experiments described here the phosphate concentration has been varied between 5.5 and 6.5 M with sulfate concentrations between 0.02 and 0.3 M. In this whole range the incorporation of phosphate can be described by a D-value of 1.5-2 10, which is 10 times lower than for DH. As pointed out in section 3.2, this can be caused by differences in crystal structure of HH and DH or in solution composition, or by the higher temperature of HH crystallization. 

The supersaturation is too low in all experiments to be measured accurately, but it seems reasonable to assume that the effect of residence time is imposed through the kinetics. Another observation is that the D-value for cadmium uptake in anhydrite is about ten times higher than in HH or DH. An explanation for this higher D seems to be related to the crystal structures of the calcium sulfates. Only the AH structure matches with an anhydrous CdSO phase, while no hemi- or dihydrate phase of CdS04 exists. 

Both compounds crystallize with the cadmium diiodide structure (space group P3ml) as previously reported on polycrystalline samples.3 For platinum disulfide, ao = 3.542(1) A and c0 = 5.043(1) A, and for platinum ditelluride, a0 = 4.023(1) A and c0 = 5.220(3) A. Direct chemical analysis for the component elements was not carried out. Instead, precision density and unit-cell determinations were performed to characterize the samples. The densities of both compounds as determined by a hydrostatic technique with heptadecafluorodeca-hydro-l-(trifluoromethyl)naphthalene as the density fluid4 indicated that they are slightly deficient in platinum. For platinum disulfide, = 7.86 g/cm3 and Pmeas = 7.7(1) gm/cm3, and for platinum ditelluride, p = 10.2 gm/cm3 and Pmeas = 9.8(1) gm/cm3. In a typical experiment an emission spectrum of the platinum disulfide showed that phosphorus was present in less than 5 ppm. A mass spectroscopic examination of the platinum ditelluride revealed a small doping by sulfur (less than 0.4%) and traces of chlorine and phosphorus (less than 100 ppm). 

FIGURE 1.40 (a) The crystal structure of cadmium iodide, CdU (b) the structure of the layers in CdU and CdCl2 the halogen atoms lie in planes above and below that of the metal... 

Cadmium Sulfide. CdS [1306-23-6] is dimorphic and exists in the sphalerite (cubic) and wurtzite (hexagonal) crystal structures (40). At very high pressures it may exist also as a rock-salt structure type. It is oxidized to the sulfate, basic sulfate, and eventually the oxide on heating in air to 700°C, especially in the presence of moisture (9). 

The octahedral radii of the table are applicable to complex ions such as [PtCle]—. The radius sum Pt(IV)—Cl is 2.30 A, and the several reported experimental values for salts of chloroplatinic acid range from 2.26 A to 2.35 A. The radii can also be applied to the sulfides, selen-ides, and tellurides of quadrivalent palladium and platinum (PdS2, etc.), which crystallize with the cadmium iodide structure, consisting of layers of MX octahedra so packed together that each X is common to three octahedral complexes. The average deviation between radius sums and reported distances for these substances is about 0.02 A. 

From the observed values of interatomic distances in complex ions such as [SnCh]—, [PbBr0], and [SeBr ]— and from crystals such as TiS2 with the cadmium iodide structure the octahedral radii given in Table 7-17 have been obtained. These correspond not to cPsp bonds, involving d orbitals of the shell within the valence shell, but to sp d2 orbitals, use being made of the unstable d orbitals of the valence shell itself. 

This brings us to a class of compounds too often overlooked in the discussion of simple ionic compounds the transition metal halides. In general, these compounds (except fluorides) crystallize in structures that are hard to reconcile with the structures of simple ionic compounds seen previously (Figs. 4.1-4.3). For example, consider the cadmium iodide structure (Fig. 7.8). It is true that the cadmium atoms occupy octahedral holes in a hexagonal closest packed structure of iodine atoms, but in a definite layered structure that can be described accurately only in terms of covalent bonding and infinite layer molecules. 

The crystal structure of [Cd(GlyGly)(Im)Cl] has been reported72 and shown to involve dimeric units with a distorted octahedral geometry about each metal atom this complex has also been studied in a 13C NMR investigation of a range of nucleoside and peptide complexes of cadmium(II).430... 

Crystal structures of the benzotriazole complexes [Zn(HL)Cl2] and [Zn2L4] (HL = benzotriazole 62) have been reported the former compound has the metal in a tetrahedral N2C12 environment (Zn—N, 2.014, 2.034 A Zn—Cl, 2.241, 2.235 A) and the latter is a polymeric species.441 The complex [H2L]2[ZnCU] (HL = 62) has also been described it is isostructural with the tetrachlorocobaltate(II) analogue, which has previously been structurally characterized.441 The synthesis and powder diffraction pattern for [ZnL Cy (L = 62) have also been reported.442 Complexes of the type MX2L2 (M - Zn, X = Cl, Br, I or SCN M = Cd, X = Cl L = allyl or 3,5-dimethylpyrazole) have been synthesized where L is 3,5-dimethylpyrazole, cadmium also forms the complexes (CdBr2L3 and CdI2L4. When L is allylpyrazole, alkene coordination is not observed thiocyanate is N-bonded.443,444... 

The involvement of zinc in nicotinamide-based hydride-transfer reactions has led to numerous studies of Group IIB complexes of pyridine carboxylic acid derivatives. Cadmium complexes of 2-pyridinecarboxylic acid, 5 3-pyridinecarboxylic add497 and 3-pyridinecarboxamide498 have been reported. The crystal structure of [Cd(HC02)2L2(H20)2] (L = 3-pyridinecarboxamide) has also been described the metal is in an octahedral environment in which the amide acts as a monodentate N donor.498... 

The crystal structure of Cd(S04) has been redetermined.672 The cadmium atom in Cd(S04) is in a very distorted Cd04 tetrahedron, with the O—Cd—O angles varying from 88.1 to 142.7. In contrast, the structure of Cd2(NH4)2(S04)3 contains two inequivalent octahedral sites for Cd2+, and is essentially isostrubtural with K2Mg(S04)3. It is found that Mn2+ may be preferentially incorporated (82%) into the site with the shorter average cation—oxygen distance.673... 

The crystal structure of cadmium(II) formate dihydrate has been determined768 and consists of a three-dimensional polymer with each cadmium octahedrally coordinated. In a two-dimensional plane, the formates bridge in an anti,anti configuration, while in the perpendicular plane, the bridging is in a syn,anti manner. Water molecules occupy the remaining coordination... 

The crystal structure of cafena-bis[ -(Af-methylpiperidinium-4-thiolato)]cadmium(II) perchlorate dihydrate827 involves infinite chains of cadmium atoms, each of them tetrahedrally coordinated to four sulfur atoms of four different Af-methylpiperidinium-4-thiolato groups. Each sulfur atom bridges two consecutive cadmium atoms, r(Cd—S) = 2.548 A. 

---