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The crystal structures of the benzene and bromobenzene inclusion compounds of tris(o-pheny1enedioxy)phosphonitrile trimer have been determined using three-dimensional methods. The compounds are isomorphous, with a hexagonal unit cell containing two phosphonitrilic host mofecules and approximately one included guest molecule. The centres of the phosphonitrilic rings are located on the special positions (1/3, 2/3, z ) and (2/3, 1/3, z + 1/2) of space group P6,. The structural arrangement of the host molecules forms a channel along the c axis, and the guest molecules are in disordered positions within this channel.Least-squares refinement of the host molecule parameters only, employing anisotropic correction factors, led to final R values of 0.073 and 0.083 for the benzene and bromobenzene compounds, respectively. The phosphonitrilic ring is planar, and the average bond distance in the ring is 1.575 * 0.002 8. The 0-P-0 angle of 97" is smaller than the equivalent angle in simply substituted phosphonitrilic trimers, but is close to the angle of 99" reported for methyl ethylene phosphate.TRIS (O-PHENYLENEDIOXY)PHOSPHONITRILE trimer (I) unit cell. The inclusion compounds show hexagonal forms crystalline inclusion compounds when recrystal-symmetry with two host molecules per unit cell accomlised from organic solvents. Some of the properties of panied by approximately one guest mo1ecule.l these compounds have been discussed in a recent Payer.l X-Ray sing1e crysta1 and powder diffraction data graphic Association, Gatlinburg, Tern., June 27-July 2, 1965.monoclinic or triclinic structure with an eight-molecule 86, 5140.

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Bulk cadmium stannate, Cd2SnO4, normally crystallizes in the orthorhombic system. Cadmium stannate obtained from sputtered thin films and from a high-temperature, high-pressure procedure has now been shown, on the basis of an X-ray diffraction investigation, to crystallize in the cubic system. The lattice parameter of the face-centered cell is 9.143 + @001 A. The data are consistent with a spinel structure, analogous to cadmium indate.The preparation and properties of thin films of cadmium stannate, Cd2SnO4, deposited on fused quartz and other substrates has been described by Nozik (1972) and by Haacke (1976). These films have been found to be promising candidates for transparent electrodes and for coatings in solarheat collectors by Haacke (1976Haacke ( ,1977. In the course of this work, X-ray diffraction patterns of the films, in situ, were obtained by mounting the substrate in the sample post of a powder diffractometer. The patterns usually showed several strong lines, although the relative intensities of the lines varied among the different film samples. There was no agreement between the interplanar spacings of the thin-film patterns and those reported by Tr6mel (1969) for the orthorhombic form of bulk cadmium stannate. It was not possible to find agreement with any of the tin or cadmium oxide diffraction patterns.In one case, a small portion of film deposited on singlecrystal sodium chloride was freed from its substrate. This material was ground and powder patterns were obtained both with a Guinier-Nonius focusing camera and with a standard 114.6 mm diameter Debye-Scherrer camera. Cu K:t radiation was employed, nickel-filtered when used with the Debye-Scherrer camera. These patterns, which showed some line broadening, were also clearly different from that of orthorhombic cadmium stannate. Further investigation showed, however, that the patterns of the film material, with the exception of one weak line, showed substantial agreement both in interplanar spacings and intensities with the powder pattern of cadmium indate, Cdln204. The latter had been reported by Skribljak, Dasgupta & Biswas (1959) who indexed the pattern on the face-centered cubic lattice and who proposed that Cdln204 had the inverse spinel structure. This was supported by intensity calculations.The agreement between the diffraction patterns of Cd2SnO4 and Cdln204, together with the similarity of the scattering powers of Cd 2÷, In 3÷ and Sn 4÷ and their ionic radii, suggests that CdzSnO4 also crystallizes in a spinel structure.Subsequently, examples of the spinel form of Cd2SnO4 were found in bulk samples. One of these was a preparation made from a sample of precipitated mixed hydroxides of cadmium and tin that was fired at 900 °C. The diffraction pattern of this material was also slightly broadened.A second bulk sample was prepared by fusion at hightemperature and high-pressure conditions. Bulk orthorhombic Cd2SnO4 was densely packed in an aluminum oxide crucible which was placed in a quartz ampoule. The ampoule was evacuated, sealed off, and...

Articles you may be interested inThe rotational spectrum and molecular properties of the hydrogen cyanide hydrogen bromide complex J. Chem. Phys. 78, 3494 (1983); 10.1063/1.445172 Structure of sodium cyanide by molecular beam electric resonance spectroscopy An attempt has been made to decide between the Pauling and Frenkel hypotheses for group disorder in crystals on the basis of x-ray diffraction data.Measurements of the line intensities of sodium cyanide showed that no decision could be reached between two models involving complete spherical rotation and a tetrahedral distribution of equilibrium positions. The 220 line was found to possess an anomalously large variation of intensity with temperature. A new rhombohedral form of sodium cyanide was found which can be produced only by quenching the cubic form from the vicinity of 300°C. The cubic and rhombohedral forms coexist from 20°C to 80°C. An ordered structure has been proposed for the rhombohedral phase.The diffuse scattering from a single crystal of sodium nitrate has been studied, and a diffuse maximum has been found which is believed to be a result of group disorder. This maximum shows a strong angular dependence which is incompatible with the predictions of the rotation theory. The data fit a twofold disorder model for the nitrate groups, provided that the positions have an aragonite-type of coordination with the surrounding sodium atoms, rather than the calcite coordination found in the ordered structure.