The hydrogen-bond effect on the high pressure behavior of hydrazinium monochloride

The first high pressure study of solid hydrazinium monochloride has been performed by in situ Raman spectroscopy and synchrotron X-ray diffraction (XRD) experiments in diamond anvil cell (DAC) up to 39.5 and 24.6GPa, respectively. The structure of phase I at room temperature is confirmed to be space group C2/c by the Raman spectral analysis and Rietveld refinement of the XRD pattern. A structural transition from phase I to II is observed at 7.3GPa. Pressure-induced position variation of hydrogen atoms in NH3+ unit during the phase transition is attributed to the formation of N?H...Cl hydrogen-bonds, which play a vital role in the stability and subsequent structural changes of this high energetic material under pressure. This inference is proved from the abnormal pressure shifts and obvious Fermi resonance in NH stretching mode of N2H5+ ion in the Raman experiment. Finally, a further transition from phase II to III accompanied with a slight internal distortion in the N2H5+ ions occurs above 19.8GPa, and phase III persists up to 39.5GPa. Copyright (c) 2015 John Wiley & Sons, Ltd.