Characterization of a high pressure, high temperature modification of ammonia borane (BH3NH3)
2013 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 139, no 5, 054507- p.Article in journal (Refereed) Published
At elevated pressures (above 1.5 GPa) dihydrogen bonded ammonia borane, BH3NH3, undergoes a solid-solid phase transition with increasing temperature. The high pressure, high temperature (HPHT) phase precedes decomposition and evolves from the known high pressure, low temperature form with space group symmetry Cmc2(1) (Z = 4). Structural changes of BH3NH3 with temperature were studied at around 6 GPa in a diamond anvil cell by synchrotron powder diffraction. At this pressure the Cmc2(1) phase transforms into the HPHT phase at around 140 degrees C. The crystal system, unit cell, and B and N atom position parameters of the HPHT phase were extracted from diffraction data, and a hydrogen ordered model with space group symmetry Pnma (Z = 4) subsequently established from density functional calculations. However, there is strong experimental evidence that HPHT-BH3NH3 is a hydrogen disordered rotator phase. A reverse transition to the Cmc2(1) phase is not observed. When releasing pressure at room temperature to below 1.5 GPa the ambient pressure (hydrogen disordered) I4mm phase of BH3NH3 is obtained.
Place, publisher, year, edition, pages
2013. Vol. 139, no 5, 054507- p.
IdentifiersURN: urn:nbn:se:su:diva-94045DOI: 10.1063/1.4817188ISI: 000322950500035OAI: oai:DiVA.org:su-94045DiVA: diva2:651408