Crystal structure similar

Galasso and Darby [220] prepared and investigated the oxyfluoride K2NbC>3F, which has crystal structure similar to K2Ta02F and crystallizes in a K2NiF4 type structure. The structure of the compound consists of infinite layers of octahedrons, Nb04F2, that are oriented perpendicular to the c axis, as shown in Fig. 34. 

Other examples of compounds that are considered MeX3-type compounds are lithium hexafluorotantalate (-niobate), LiTaF6 and LiTaF6, which have crystal structures similar to A1F3. Both lithium and tantalum (niobium) cations have similar ionic radii and are located in the centers of octahedrons that are composed of fluorine anions. 

Tantalum and niobium fluoride compounds that crystallize in coordination-type structures also seem to be perspective candidates for the investigation of ferroelectric properties. Ravez and Mogus-Milancovic [404] showed that some fluoride and oxyfluoride compounds with crystal structures similar to the Re03 type exhibit ferroelastic properties. For instance, ferroelastic properties were found in some solid solutions based on Nb02F and Ta02F [405,406]. 

At atmospheric pressure, solid II converts to solid I at a temperature of 291 K. Solid I is a grey semiconductor0 with a face-centered cubic crystal structure similar to that of C(diamond), Si, and Ge at atmospheric pressure. It is... 

The thiepin 13 (X = S) was found to be inert toward catalytic hydrogenation. The authors ascribe the stability of 13 (X = S) to a contribution of the charge-separated structures 13a and 13 b to the ground state of 13 (X = S) 71). An X-ray structural determination showed that 13 (X = S) is nearly planar with a disordered crystal structure similar to that of azulene 73). 

Silicon is the most popular material for photovoltaic (PV) power. Another material is gallium arsenide (GaAs), which is a compound semiconductor. GaAs has a crystal structure similar to that of silicon, but it consists of alternating gallium and arsenic atoms. It is well suited for PV applications since it has a high light absorption coefficient and only a thin layer of material is required, which reduces the cost. 

PI5.9 Boron nitride (BN) is isoelectronic with carbon and the B, C, and N atoms are about the same size. The result is that BN forms crystal structures similar to those of carbon, in that it crystallizes in a hexagonal (graphite-like hBN) and a cubic (diamond like cBN) structure. The data summarized at the end of the problem are available for the two forms of BN.17... 

Complete solid solubility requires that components have the same crystal structure, similar atomic size, electronegativity and valency. If any of these conditions are not met, a miscibility gap will occur in the solid state. 

In the HCP crystal structure, similar to the CCP, the coordination number of the lattice sites is 12, and two octahedral sites per basic hexagonal prism, that is, six per each HCP cell are present (see Figure 2.14). 

Perovskites — are a very large family of compounds with the crystal structure similar to that of (Ca, Sr) TiC>3 mineral, named after the Russian mineralogist T. A. Per-ovski (1792-1856). This structure is often called an inorganic chameleon due to the diversity of chemical compositions, structural modifications, and properties. Although most members of this family are oxidic compounds, some nitrides, carbides, halides, and hydrides also have this structure. 

M3Ta02F4 and M3Nb02F4, where M = K, Rb, Cs, form crystal structures similar to that of Rb3TiF6, which is described by Bode and Voss [189]. The structure of the compounds can be described as a tetragonally distorted cubic cell of the (NH4)3FeF6 type, the structure of which is described by Steward and Rockby [190]. 

Ceria may be dissolved in YSZ, which also has the fluorite structure. Then a driving force for reduction of Ce to Ce exist because the radius of Ce is big enough to facilitate the formation of the pyrochlore compound, CejZrjO- , which has a crystal structure similar to the fluorite but with fully ordered oxide vacancies. This tends to segregate to the grain boundaries and induces electronic conductivity into the YSZ. ... 

Octaethylporphyrin (H2OEP) and thorium complex to give a crystal structure similar to that seen with H2TPP and thorium. In Th(OEP)2, the coordination environment around the thorium is an ideal square antiprism. The replacement of phenyl groups with ethyl chains removes any steric hindrance that was present in Th(TPP)2. This is illustrated in Figure 35." ... 

The bromination of poly-DCH is of interest because the degree of bromine uptake can be controlled, by choice of experimental conditions, between 3 and 8 Br atoms per polymer repeat unit and because a crystal-to-crystal transformation is observed. Scheme 1 summarizes the reactions of liquid bromine with poly-DCH. Interaction of poly-DCH crystals with dense vapors of bromine or cyanogen bromide for months did not lead to detectable weight gain. By contrast, DCH monomer (2a), which has a crystal structure similar to the polymer (6), readily reacts with bromine vapor to give an eunor-phous material which has gainbd ca 12 Br atoms per molecule. 

There are several chemical and crystal structure similarities in the high Tc ceramic superconductors. A general feature in their... 

Some high-temperature superconductors adopt a crystal structure similar to that of perovskite (CaTiOs). The unit cell is cubic with a Ti" " ion in each comer, a Ca " ion in the body center, and 0 ions at the midpoint of each edge, (a) Is this unit cell simple, body-centered, or face-centered (b) If the unit cell edge length is 3.84 A, what is the density of perovskite (in g/cm ) ... 

Arsenic, Antimony and Bismuth. These elements are obtained by reduction of their oxides with hydrogen or carbon. For As and Sb unstable yellow allotropes, presumably containing tetrahedral As4 and Sb4 molecules, can be obtained by rapid condensation of vapors. They are easily transformed into the stable forms, and yellow Sb is stable only at very low temperatures. Bismuth does not occur in a yellow form. The normal forms of As, Sb and Bi are bright and metallic in appearance and have crystal structures similar to that of black P. When heated, the metals burn in air to form the oxides, and they react directly and readily with halogens and some other non-metals. They form alloys with various other metals. Dilute non-oxidizing acids are without effect on them. With nitric acid, As gives arsenic acid, Sb gives the trioxide and Bi dissolves to form the nitrate. 

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