title: Ab initio molecular dynamic study of solid-state transitions of ammonium nitrate.
abstract: High-pressure polymorphism and phase transitions have wide ranging consequences on the basic properties of ammonium nitrate. However, the phase diagram of ammonium nitrate at high pressure and high temperature is still under debate. This study systematically investigates the phase transitions and structural properties of ammonium nitrate at a pressure range of 5-60 GPa and temperature range of 250-400 K by ab initio molecular dynamics simulations. Two new phases are identified: one corresponds to the experimentally observed phase IV' and the other is named AN-X. Simultaneously, the lattice strains play a significant role in the formation and stabilization of phase IV', providing a reasonable explanation for experimental observation of phase IV-IV' transition which only appears under nonhydrostatic pressure. In addition, 12 O atoms neighboring the NH (N atom in ammonium cation) atom are selected as reference system to clearly display the tanglesome rotation of ammonium cation.
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Yu
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Defang
authors.initials: D
authors.lastname: Duan
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, S7N 5E2, Canada.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Liu
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Fubo
authors.initials: F
authors.lastname: Tian
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Kuo
authors.initials: K
authors.lastname: Bao
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Da
authors.initials: D
authors.lastname: Li
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Zhonglong
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Bingbing
authors.initials: B
authors.lastname: Liu
authors.affiliation: State key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Tian
authors.initials: T
authors.lastname: Cui