Studies on Molecular Dissociation and Metallization of Molecular crystals under High Pressure

1.固体氧的结构相变和金属化由固体氧在100 GPa附近的折射率的轻微增加，提出了固体氧的绝缘体-金属转变。我们观察到在96 GPa下从α相到zeta相的同构相变。这两个阶段被分配到一个单斜晶格。该转变负责固体氧的金属化。在转变过程中，单斜角和摩尔体积几乎没有变化。为了揭示金属化的机理，我们在高达110 GPa的压力下对固体氧进行了拉曼研究。在低于跃迁的压力下，清楚地观察到振动模式和振动模式，并且振动模式的频率单调增加，但是在高于跃迁的压力下没有观察到任何拉曼活性模式的峰。频率的单调增加表明，氧分子没有解离的过渡。我们认为固体氧的金属化是通过能带重叠机制实现的。我们还提出了空间群为C_2/m_2。Se和CX_4（X=F，Cl，Br）的压致结构相变研究了CX_4（X = F，Cl，Br）化合物的压致结构相变。硒在环境条件下有几种同素异形体。研究了这些修饰的分子解离和金属化。

1. Structural Phase Transition and Metallization of Solid OxygenThe insulator-metal transition of solid oxygen has been suggested from the slight increase of the refrectivity at pressure around 100 GPa. We have observed the isostructural phase transition from the epsilon phase to the zeta phase at 96 GPa. The both phases are assigned to a monoclinic lattice. The transition is responsible for the metallization of solid oxygen. At the transition, the monoclinic angle and the molar volume were scarcely changed. To reveal the mechanism of the metallization, we have performed Raman studies on solid oxygen under pressure of up to 110 GPa. At pressure of below the transition, a vibrational mode and librational modes were clearly observed and the frequency of the vibrational mode monotonically increased, but any peak of the Raman active modes was not observed at pressure of above the transition. The monotonical increase of the frequency suggests that oxygen molecules were not dissociated at the transition. Now we conclude that the metallization of solid oxygen is realized through the mechanism of the band overlapping. We also proposed the space group of the epsilon phase as C2/m.2. Pressure-induced structural phase transition of Se and CX_4 (X=F,Cl, Br)Pressure-induced structural phase transitions of CX_4 compounds (X=F,C1 and Br) have been investigated. Selenium has several allotropic modifications at ambient conditions. The molecular dissociation and the metallization of these modifications were also studied.