High pressure synchrotron x-ray diffraction and Raman scattering studies of ammonium azide

Ammonium azide (NH4N3) has been studied by in situ high-pressure X-ray diffraction and Raman scattering at room temperature. NH4N3 exhibits strong hydrogen bonding features with compression. The hydrogen bond weaken with increasing pressure due to the bending of N-H center dot center dot center dot N bond, leading to the increase of N-H stretch frequency and rotation of azide anions at 2b and 4h Wyckoff positions up to 2.9 GPa. The orientation of azide anions obviously influences the compressibility properties of NH4N3. The phase transition involves rotation of azide anions and a proximity of a and c, temporally assigned as a reversible second-order orthorhombic-to-tetragonal transition. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4798336]