Pressure-Induced Phase Transition in Hydrogen-Bonded Supramolecular Structure: Ammonium Formate
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- 作者：Lei Kang ; Kai Wang ; Shourui Li ; Jing Liu ; Ke Yang ; Bingbing Liu ; Bo Zou
- 刊名：Journal of Physical Chemistry C
- 出版年：2014
- 出版时间：April 24, 2014
- 年：2014
- 卷：118
- 期：16
- 页码：8521-8530
- 全文大小：572K
- 年卷期：v.118,no.16(April 24, 2014)
- ISSN：1932-7455
文摘
High-pressure behaviors of hydrogen-bonded supramolecular structure, ammonium formate (NH4+COOH鈥?/sup>, AF), have been investigated under pressure by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy up to 20 GPa. Under ambient conditions, AF exhibits three-dimensional hydrogen-bonded networks with two molecules crystallize in a monoclinic unit cell of space group Pc. A structural phase transition can be identified at around 1.8 GPa, as indicated by the abrupt changes in Raman spectra as well as the pressure dependence of major Raman modes. Furthermore, two new N鈥揌 stretching modes emerge, indicative of the construction of new hydrogen bonds. Rearrangement of the hydrogen-bonded networks is also deduced by the obvious changes of N鈥揌 stretching modes both in position and intensity. The reversible phase transition is confirmed by in situ synchrotron XRD experiments with the emergence of a new set of diffraction pattern. The high-pressure phase is found to have a structure with a monoclinic unit cell (space group P21) containing two molecules. The structural transformation is proposed to be a result of the rearrangement of the hydrogen-bonded networks. Detailed mechanism for the phase transition, high-pressure behaviors of hydrogen bonds, as well as the cooperativity of different noncovalent interactions are presented and discussed.