Cuprite structure

The cuprite structure consists of a body-centered cubic (bcc) array of oxygen atoms, and the copper atoms occupy centers of four of the eight cubes into which the bbc cell may be divided. In this partially covalent structure, copper has a linear coordination and oxygen a tetrahedral coordination. 

The Cu(100) surface shows in 0.1 M NaOH a similar anodic and cathodic peak both at E = —0.8 V [137] however, no reconstruction of the surface could be found. This is presumably not necessary because the Cu(100) surface is less densely packed in comparison with Cu(lll) and matches already the cuprite structure. Similarly, the close match of the anodic and cathodic peaks without a hysteresis is an additional indication for a faster adsorption process, whereas the surface reconstruction of Cu(lll) with the dilfusion of the Cu atoms to the step edges slows the adsorption process. The anodic film forms at first also a granular structure and a final crystalline film. First STM studies suggest an orientation of Cu(100) parallel to Cu2O(100) with a distance parameter of 0.3 nm which corresponds again to the Cu Cu distance within the cuprite structure. 

White Cd(CN)2 is sparingly soluble in water, except in the presence of CN ions, owing to the formation of soluble anionic complexes. On heating it darkens and decomposes at about 200 °C. Cd(CN)2, like Zn(CN)2, has a cubic anti-cuprite structure. Colorless cadmium thiocyanate is sparingly soluble in water, ethanol, and liquid ammonia. In the solid, Cd + is surrounded by an N2S4 octahedron. Cadmium thiocyanate polymers exhibit highly anisotropic physical properties. Yellow Cd(N3)2 is prepared by mixing solutions of Cd(N03)2 and NaNs. The crystals are orthorhombic and decompose with detonation when heated. Cadmium pseudohalides (see Pseudohalide) may be prepared by metathesis (equation 3). 

The formation of passive oxide films on the (111) surfaces of Cu and Ni has also been studied in detail by SXS [94, 95]. Measurements of Cu(lll) in 0.1 M NaCl04 (at pH 4.5) showed that the oxide exhibited a crystalline cuprite structure (CU2O) that was epitaxially aligned with the underlying Cu substrate [94]. Although a similar oxide structure was observed for oxidation in air, there were some key differences in the structure of the aqueous oxide. In particular it was found that a preferred reversed orientation of the oxide film was formed, and this indicated that oxide growth occurs at the interface between the oxide and the Cu(lll) surface... 

Ba, Pb) and the layered cuprite structures of the high temperature superconductors (see Section 26.10), neither of which are completely imderstood. One of the major problems in utilizing CMR in practical devices is that, in the materials discovered thus far, the effect occurs only at temperatures well below ambient. 

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