1. Hydrogen Desorption Exceeding Ten Weight Percent from the New Quaternary Hydride Li3BN2H8
2. The capillary was mounted on a Stoe IPDS II diffractometer equipped with an image-plate detector and a Mo X-ray tube. The segment giving the best individual diffracting spots and practically no Debye rings was selected for measurement. 180° ω oscillation images with an increment of 1° were collected at 20 °C with 1 min of exposure and a crystal-to-detector distance of 120 mm. All diffraction intensities could be indexed3aby assuming five randomly intergrown domains, each possessing a body-centered-cubic lattice witha∼ 10.7 Å. The four largest domains were accounted for during the intensity integration. Although overlapping intensities were omitted, highly redundant data sets (∼99% completeness; on average 13 equivalents per unique reflection) were obtained for two domains. The data were corrected for Lorentz factor and polarization effects. Absorption correction was not applied. Cell parameters were obtained by a least-squares refinement based on reflection angles in the range of 4 < 2θ < 54°. No significant variation of the average intensity during the measurement was observed. The mergingRfactor suggested Laue symmetrym3̄, and the systematic absences indicated the possible space groupsI23,I213, andIm3̄. Structure solution by direct methods3bat the nominal composition Li3BN2H8,Z= 10, failed for all three space groups. However, a satisfactory model was obtained by FOX3cin space groupI213, by allowing an excess of N, B, and Li atoms. The latter were partially merged during global optimization, yielding one N, one B, and three symmetry-independent Li atom sites. Subsequent difference Fourier maps3brevealed four H atom positions. At this stage, the true composition of the domains turned out to be Li4BN3H10with eight formula units per cell (Z= 8), yielding a calculated density of 0.99 g·cm-3, which was close to the experimental value of 0.96 g·cm-3.1A full-matrix least-squares refinement onF 2was performed on positional and thermal parameters for all atoms (anisotropic for N, B, and Li) by usingSHELXL-97.3bNeutral atom scattering factors were used, yielding refined occupancies that were very close to 100%. Reduced cell calculations and a noncrystallographic symmetry check (PLATON, 2003)3ddid not indicate higher lattice symmetry or missed symmetry elements. A small twin component (<1%) related to the main domain by a 2-fold axis at 1/2, 1/2, 0 (supergroupI4132) was modeled with an extra parameter. No warnings for twinning or superstructure were observed thereafter. Because of the absence of anomalous scatterers for Mo Kα radiation, an absolute structure could not be determined. (a) Stoe & Cie,X-RED and X-Area Software; Stoe & Cie: Darmstadt, Germany, 2003. (b) Sheldrick, G. M.SHELXS97 and SHELXL97. Programs for the solution andrefinement of crystal structures; University of Göttingen: Göttingen, Germany, 1997. (c) Favre-Nicolin, V.; Cerny, R.J.Appl. Crystallogr.2002,35, 734. (d) Spek, A. L.PLATON. A Multipurpose Crystallographic Tool; University of Utrecht: Utrecht, The Netherlands, 2003.
3. STRUCTURE TIDY– a computer program to standardize crystal structure data
4. Lithium boro-hydride LiBH4