Behavior of Decomposed Ammonia Borane at High Pressure up to ~10 GPa

Sun, Yong Zhou; Chen, Jiu Hua; Drozd, Vadym; Najiba, Shah

doi:10.4028/www.scientific.net/msf.783-786.1829

Cited by 1 publication

(2 citation statements)

References 29 publications

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“…The polymorphic structure of NH 3 BH 3 has been studied previously as outlined below. − In the ambient-pressure phase (AP, α-NH 3 BH 3 ), the molecules of NH 3 BH 3 are arranged in parallel to the c -axis, forming an I 4 mm structure. As the molecule rotates around the B–N axis and the hydrogen atoms become disordered, the H–H distances between the adjacent molecules are distributed at ∼2.0 ± 0.4 Å.…”

Section: Introductionmentioning

confidence: 99%

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Observation of Dihydrogen Bonds in High-Pressure Phases of Ammonia Borane by X-ray and Neutron Diffraction Measurements

et al. 2021

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High-pressure X-ray and neutron diffraction analyses of an ambient-pressure phase (AP) and two high-pressure phases (HP1 and HP2) of ammonia borane (i.e., NH3BH3 and ND3BD3) were conducted to investigate the relationship between their crystal structures and dihydrogen bonds. It was confirmed that the hydrogen atoms in AP formed dihydrogen bonds between adjacent molecules, and the H–H distance between the hydrogen atoms forming this interaction was shorter than 2.4 Å, which was nearly 2 times larger than the van der Waals radius of hydrogen. In the case of half of the hydrogen bonds, a phase transition from AP to the first high-pressure phase (HP1) at ∼1.2 GPa resulted in an increase in the H–H distances, which suggested that the dihydrogen bonds were broken. However, when HP1 was further pressurized to ∼4 GPa, all of the H–H distances became shorter than 2.4 Å again, which implied the occurrence of pressure-induced re-formation of the dihydrogen bonds. It was speculated that the re-formation was consistent with a second-order phase transition suggested in previous studies by Raman spectroscopy and X-ray diffraction measurement. Furthermore, at ∼11 GPa, HP1 transformed to the second high-pressure phase (HP2), and its structure was determined to be P21 (Z = 2). In this phase transition, the inclination of the molecule axis became larger, and the number of types of dihydrogen bonds increased from 6 to 11. At 18.9 GPa, which was close to the upper pressure limit of HP2, the shortest dihydrogen bond decreased to ∼1.65 Å. Additionally, the X-ray diffraction results suggested another phase transition to the third high-pressure phase (HP3) at ∼20 GPa. The outcomes of this study confirmed experimentally for the first time that the structural change under pressure causes the breakage and re-formation of the dihydrogen bonds of NH3BH3.

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Section: Introductionmentioning

confidence: 99%

“…Theoretical calculations have also been used to predict other transitions to P 2 1 ( Z = 2) at 15 GPa and P 2 1 ( Z = 4) at 50 GPa as well as transitions to Ama 2 at 6 GPa and P 2 1 / m at 22 GPa . Moreover, experiments and calculations at high pressures and high temperatures − and low temperatures − have been reported.…”

Section: Introductionmentioning

confidence: 99%