title: Pressure-induced isosymmetric phase transition in sulfamic acid: a combined Raman and x-ray diffraction study.
abstract: High-pressure behaviors of hydrogen-bonded molecular crystal, sulfamic acid (NH3(+)SO3(-), SA), have been investigated using Raman spectroscopy and synchrotron X-ray diffraction (XRD) techniques up to the pressure of ~20 GPa. Under ambient conditions, molecules of SA are arranged in puckered layers and held together by hydrogen bonding and electrostatic interactions. It is proved by the Raman results that SA undergoes the molecular conformation changes in the pressure range 8.1-10.2 GPa. Then between 10.2 and 12.7 GPa, a phase transition is observed in both Raman and XRD patterns. Both the ambient and high-pressure phases of SA crystallize in Pbca symmetry with similar unit-cell dimensions. The mechanism of the phase transition involves relative movements of adjacent hydrogen-bonded molecules, accompanied by the rearrangement of hydrogen bonds and the enhancement of electrostatic interactions.
authors.affiliation: State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Shourui
authors.initials: S
authors.lastname: Li
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Bingbing
authors.initials: B
authors.lastname: Liu
authors.forename: Guangtian
authors.initials: G
authors.lastname: Zou
authors.forename: Bo
authors.initials: B
authors.lastname: Zou
mesh_terms: D006860:Hydrogen Bonding; D044367:Phase Transition; D011312:Pressure; D013059:Spectrum Analysis, Raman; D013451:Sulfonic Acids / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D013451:Sulfonic Acids; C005741:sulfamic acid