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Elastic properties study of single crystal NH 3 up to 26 GPa
Author(s) -
Li Fangfei,
Duan Defang,
Li Min,
Ma Chunli,
Cui Qiliang,
Cui Tian,
Zhou Qiang,
Li Xiaodong,
Li Yanchun,
Liu Jing,
Zou Guangtian
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.3068
Subject(s) - orthorhombic crystal system , raman spectroscopy , bulk modulus , elastic modulus , chemistry , raman scattering , phase (matter) , phase transition , materials science , thermodynamics , analytical chemistry (journal) , crystallography , crystal structure , optics , composite material , physics , organic chemistry , chromatography
Single crystal Brillouin and Raman scattering measurements on NH 3 in a diamond anvil cell have been performed under pressures up to 26 GPa at room temperature. The pressure dependencies of acoustic velocity, adiabatic elastic constants, and bulk moduli of ammonia from liquid to solid III and solid IV phase have been determined. All the nine elastic constants in orthorhombic structure phase IV were presented for the first time, each elastic constant grows monotonously with pressure and a crossover of the off‐diagonal moduli C 12 and C 13 was observed at around 12 GPa because of their different pressure derivative values. We also performed ab initio simulations to calculate the bulk elastic moduli for orthorhombic ammonia, the calculated bulk moduli agree well with experimental results. In Raman spectra the very weak bending modes ν 2 and ν 4 for orthorhombic ammonia are both observed at room temperature, a transition point near 12 GPa is also found from the pressure evolution of the Raman bands. Copyright © 2011 John Wiley & Sons, Ltd.