A computer program has been written with the aim of calculating powder patterns without the use of crystallographic tables. This has been achieved by deriving all symmetry information such as general equivalent positions from the Hermann-Mauguin space-group symbols, by calculating automatically the multiplicities of special positions and by storing the necessary constants, such as scattering factor tables, anomalous dispersion correction terms and X-ray wavelengths in the program. Owing to the very restricted amount of input data this program is especially suited for users with a limited knowledge of crystallography.

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Alkali borohydrides MBH 4 and their deuterides have been investigated by X-ray and neutron powder diffraction (M = K, Rb, Cs) and by infrared and Raman spectroscopy (M = Na, K, Rb, Cs). At room temperature the compounds crystallize with a cubic high temperature (HT) structure having Fm3m symmetry in which the [BH 4 ] − complexes are disordered. At low temperature (LT) the potassium compound transforms into a tetragonal low temperature structure having P4 2 /n mc symmetry in which the [BH 4 ] − complexes are ordered such as in the isotypic sodium congener. The B-H distances within the complex as measured on the deuteride at 1.5 K are 1.205(3) Å. Indications for a partial ordering in the rubidium and cesium compounds exist but are not sufficient for a full structural characterization. Infrared and Raman spectra at room temperature are fully assigned for both hydrides and deuterides, including the overtones and combination bands, the Fermi resonance type interactions and the 10 B to 11 B splitting due to the presence of natural boron in the samples.

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Polycrystalline LiBH has been studied by Raman spectroscopy in the temperature interval 295-412 K and the frequency range 4 21 2 2700-130 cm. The Raman active modes are consistent with the presence of a (BH) ion having a distorted tetrahedral configuration. 4 As the temperature is increased the sudden disappearance of mode splitting points to the onset of a structural phase transition that leads to 2 a higher local symmetry of the (BH) tetrahedron. The transition occurs at |384 K, is of first-order and has a hysteresis of about 8 K. A 4 strong and discontinuous broadening of bands remaining after the transition suggests the onset of large vibrational amplitudes of the 2 (BH) tetrahedra about their trigonal axis. 4

X-ray data on single crystals of the quaternary metal hydride near the composition LiB(0.33)N(0.67)H(2.67), previously identified as "Li3BN2H8", reveal that its true composition is Li4BN3H10. The structure has body-centered-cubic symmetry [space group I2(1)3, cell parameter a = 10.679(1)-10.672(1) Angstroms] and contains an ordered arrangement of BH4- and NH2- anions in the molar ratio 1:3. The borohydride anion has an almost ideal tetrahedral geometry (angleH-B-H approximately 108-114 degrees), while the amide anion has a nearly tetrahedral bond angle (angleH-N-H approximately 106 degrees). Three symmetry-independent Li atom sites are surrounded by BH4- and NH2- anions in various distorted tetrahedral configurations, one by two B and two N atoms, another by four N atoms, and the third by one B and three N atoms. The Li configuration around B is nearly tetrahedral, while that around N resembles a distorted saddlelike configuration, similar to those in LiBH4 and LiNH2, respectively.

87191-41-1; TeF5N(I)CF3, 98720-72-0; TeF5N(CF3)C(0)CH3, 98720-73-1; (TeF,),NCF,, 87191-42-2; TeFSN(SF5)CF3, 98720-74-2; TeF5N-(CF,)CH,CH,Br, 98720-75-3; TeF,N=C(CI)OCH,, 98720-76-4; Te-24, Mg2CoHS and its deuteride have been prepared as black crystalline solids by a sintering technique at temperatures between 620 and 770 K and hydrogen (deuterium) pressures between 40 and 60 bar. X-ray and neutron powder diffraction data recorded at room temperature suggest a tetragonally distorted CaF,-type metal atom structure (for the deuteride a = 4.463 (4) A, c = 6.593 (6) A, space group P 4 / n m m , and 2 = 2). The D atoms surround the Co atoms in an ordered square-pyramidal configuration (d[Co-D] = 1.590 (17) A (apical) and 1.515 (3) A (basal)). The structure transforms at 488 (5) K into a disordered cubic modification ( a = 6.453 (6) A, at 498 K). The heat of dissociation of the hydride as measured from pressure-composition isotherms is 86 (5) kJ/mol of H,. The electrical resistivity suggests nonmetallic behavior.