Experimental Verification of the High Pressure Crystal Structures in NH₃BH₃

Journal Article · Thu Jun 26 04:00:00 EDT 2014 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4884819· OSTI ID:1229076

Huang, Yanping ^[1]; Huang, Xiaoli ^[1]; Zhao, Zhonglong ^[1]; Li, Wenbo ^[1]; Jiang, Shuqing ^[1]; Duan, Defang ^[1]; Bao, Kuo ^[1]; Zhou, Qiang ^[1]; Liu, Bingbing ^[1]; Cui, Tian ^[1]

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1. Jilin Univ., Changchun (China)

We performed a detailed study with high-pressure on NH₃BH₃ and its been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure (α-NH₃BH₃) to a high pressure Cmc2₁ phase (β-NH₃BH₃) at 2.14 GPa, and further into a monoclinic P21 (Z = 2) phase (γ-NH₃BH₃) at 9.67 GPa. Fitting the measured volumetric compression data to the third order Birch-Murnaghan equation of state reveals a bulk modulus of B ₀ = 9.9 ± 0.5 and 17.0 ± 3.0 GPa (with fixed B ₀ ' = 4) for the β-NH₃BH₃ below and above 5 GPa, respectively. Still, with the splitting of the NBH rock mode in Raman experiment, it is concluded that a second-order isostructural phase transition occurs at 5 GPa. Analyzing the dihydrogen bonding framework, the origin of the isostructural phase transition is attributed to the number of dihydrogen bondings per molecule in the Cmc2₁ phase increasing from 12 to 14 at 5 GPa.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• OSTI ID: 1229076
• Report Number(s): BNL--111151-2015-JA
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 24 Vol. 140; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE