Abstract In this paper the structural and vibrational properties of intercalated fluorine graphite (C4F)n under compression up to 40 GPa are investigated by means of Raman spectroscopy, X-ray diffraction and ab initio calculations. The theoretical study was performed within the framework of the density functional theory, taking into account van der Waals corrections to the total energy. We studied the effect of anisotropic and isotropic deformation on the crystal properties, in relation to the layered structure of the sample and in particular to the C F bonding. The evolution with pressure of the phonon modes at the center of the Brillouin zone was calculated and compared with experimental data. Both our experimental data and theoretical models indicate that a structural transition occurs around 10 GPa. Above this pressure the (C4F)n structure becomes dynamically unstable, characterized by a “soft mode” and a change in symmetry due to anisotropic strain components.

中文翻译：

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高压下的氟-石墨插层化合物 (C 4 F) n：实验和理论研究

摘要 在本文中，通过拉曼光谱、X 射线衍射和从头计算，研究了夹层氟石墨 (C4F)n 在高达 40 GPa 压缩下的结构和振动特性。理论研究是在密度泛函理论的框架内进行的，同时考虑了对总能量的范德华修正。我们研究了各向异性和各向同性变形对晶体特性的影响，与样品的层状结构有关，特别是与 CF 键合。计算了布里渊区中心声子模式随压力的演变并与实验数据进行了比较。我们的实验数据和理论模型都表明结构转变发生在 10 GPa 左右。