부산대학교 도서관

Abstract: To investigate the previously reported low-temperature phase transition in rubidium borohydride (RbBH4) near 48.5K, we carried out neutron powder diffraction and vibrational spectroscopy measurements both above and below this temperature on an isotopically-enriched sample of Rb11BD4. Our diffraction data reflected an average cubic structure with BD4 − anion orientational disorder at all temperatures, with no hint of extra Bragg peaks due to long-range orientational order below the transition temperature as reported by others. These structural results and careful analysis of torsional vibrations in RbBD4 corroborate the results of prior neutron vibrational spectroscopy measurements suggesting that the low-temperature RbBH4 structure indeed possesses some orientational ordering of the BH4 − anions, but of a shorter-ranged nature insensitive to powder diffraction methods. [Copyright &y& Elsevier]