title: Pressure-induced structural transformations and polymerization in ThC2.
abstract: Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC2.
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.|Institute of Theoretical Physics, Department of Physics, East China Normal University, Shanghai 200241, China.
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Cun
authors.initials: C
authors.lastname: Yu
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Changying
authors.initials: C
authors.lastname: Wang
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.|Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Cuilan
authors.initials: C
authors.lastname: Ren
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Baoxing
authors.initials: B
authors.lastname: Sun
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Huai
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Ruobing
authors.initials: R
authors.lastname: Xie
authors.affiliation: Institute of Theoretical Physics, Department of Physics, East China Normal University, Shanghai 200241, China.
authors.forename: Xuezhi
authors.initials: X
authors.lastname: Ke
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.|Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Xu