Pressure-induced structural changes in NH{sub 4}Br

Journal Article · Fri Aug 14 04:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4927782· OSTI ID:22493512

Huang, Yanping; Huang, Xiaoli; Li, Wenbo; Wang, Lu; Wu, Gang; Zhao, Zhonglong; Duan, Defang; Bao, Kuo; Zhou, Qiang; Liu, Bingbing; Cui, Tian ^[1]

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1. State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China)

We report angle dispersive X-ray diffraction (XRD) measurements and Raman spectroscopy on NH{sub 4}Br up to 70.0 GPa at room temperature. Three thermodynamically stable phases (phases II, IV, and V) are confirmed and a new possible phase (phase VI) of P2{sub 1}/m symmetry is proposed whose structure was established from Rietveld refinement of synchrotron XRD data for the first time. The phase sequence observed in NH{sub 4}Br is in accordance with phase II → IV → V → VI. Phase V transforms into phase VI at about 57.8 GPa with a huge volume reduction of 30%. Still, the intramolecular distances are analyzed to better understand the nature of structures. The H–H interactions become markedly more important as the N–Br distances are compacted, which is probably the reason of the kink of symmetric stretching band (ν{sub 1}) at the transition pressure.

• OSTI ID: 22493512
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 6 Vol. 143; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMMONIUM COMPOUNDS
BROMIDES
INTERMOLECULAR FORCES
MONOCLINIC LATTICES
PHASE STABILITY
PHASE STUDIES
PHASE TRANSFORMATIONS
PRESSURE RANGE GIGA PA
RAMAN SPECTROSCOPY
SYMMETRY
TEMPERATURE RANGE 0273-0400 K
X-RAY DIFFRACTION