Zhu Qiang, Oganov Artem R, Zeng Qingfeng
Department of Geosciences, Stony Brook University, Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, NY 11794, USA.
1] Department of Geosciences, Stony Brook University, Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, NY 11794, USA [2] Department of Problems of Physics and Energetics, Moscow Institute of Physics and Technology, 9 Institutskiy lane, Dolgoprudny city, Moscow Region, 141700, Russia [3] School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, 710072, China.
Sci Rep. 2015 Jan 22;5:7875. doi: 10.1038/srep07875.
Alkali halides MX, have been viewed as typical ionic compounds, characterized by 1:1 ratio necessary for charge balance between M(+) and X(-). It was proposed that group I elements like Cs can be oxidized further under high pressure. Here we perform a comprehensive study for the CsF-F system at pressures up to 100 GPa, and find extremely versatile chemistry. A series of CsFn (n ≥ 1) compounds are predicted to be stable already at ambient pressure. Under pressure, 5p electrons of Cs atoms become active, with growing tendency to form Cs (III) and (V) valence states at fluorine-rich conditions. Although Cs (II) and (IV) are not energetically favoured, the interplay between two mechanisms (polyfluoride anions and polyvalent Cs cations) allows CsF2 and CsF4 compounds to be stable under pressure. The estimated defluorination temperatures of CsFn (n = 2,3,5) compounds at atmospheric pressure (218°C, 150°C, -15°C, respectively), are attractive for fluorine storage applications.
碱金属卤化物MX一直被视为典型的离子化合物，其特征是M(+)和X(-)之间电荷平衡所需的1:1比例。有人提出，像Cs这样的第一族元素在高压下可以进一步被氧化。在此，我们对CsF-F体系在高达100 GPa的压力下进行了全面研究，发现了极其多样的化学性质。一系列CsFn（n≥1）化合物预计在常压下就已经稳定。在压力下，Cs原子的5p电子变得活跃，在富氟条件下形成Cs(III)和(V)价态的趋势不断增加。尽管Cs(II)和(IV)在能量上并不占优势，但两种机制（多氟阴离子和多价Cs阳离子）之间的相互作用使得CsF2和CsF4化合物在压力下能够稳定存在。CsFn（n = 2、3、5）化合物在大气压下的估计脱氟温度（分别为218°C、150°C、-15°C）对于氟储存应用具有吸引力。
