title: Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice.
abstract: The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures.
authors.affiliation: Department of Physics, College of Science, National University of Defense Technology, Changsha 410073, Hunan, People's Republic of China.
authors.forename: Dongdong
authors.initials: D
authors.lastname: Kang
authors.forename: Jiayu
authors.initials: J
authors.lastname: Dai
authors.forename: Huayang
authors.initials: H
authors.lastname: Sun
authors.forename: Yong
authors.initials: Y
authors.lastname: Hou
authors.forename: Jianmin
authors.initials: J
authors.lastname: Yuan
mesh_terms: D015502:Absorptiometry, Photon; D006860:Hydrogen Bonding; D007053:Ice / Q000032:analysis*; D010100:Oxygen / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D007053:Ice; D010100:Oxygen