Department of Physics, South China University of Technology, Guangzhou 510640, China.
J Chem Phys. 2013 Sep 14;139(10):104302. doi: 10.1063/1.4820359.
The structural and vibrational properties of phenanthrene are measured at high pressures up to 30.2 GPa by Raman spectroscopy and synchrotron X-ray diffraction techniques. Two phase transitions are observed in the Raman spectra at pressures of 2.3 GPa and 5.4 GPa which correspond to significant changes of intermolecular and intramolecular vibrational modes. Above 10.2 GPa, all the Raman peaks are lost within the fluorescence background; however, upon further compression above 20.0 GPa, three broad peaks are observed at 1600, 2993, and 3181 cm(-1), indicating that phenanthrene has transformed into amorphous phase. Using X-ray diffraction, the structures of corresponding phases observed from Raman spectra are indexed with space groups of P2(1) for phase I (0-2.2 GPa), P2/m for phase II (2.2-5.6 GPa), P2/m+Pmmm for phase III (5.6-11.4 GPa) which has a coexistence of structures, and above 11.4 GPa the structure is indexed with space group of Pmmm. Although phenanthrene has transformed to a hydrogenated amorphous carbon structure above 20.0 GPa, these amorphous clusters still show characteristic crystalline behavior based on our X-ray diffraction patterns. Our results suggest that the long-range periodicity and the local disorder state coexist in phenanthrene at high pressures.
采用拉曼光谱和同步辐射 X 射线衍射技术在高达 30.2 GPa 的压力下测量了菲的结构和振动性质。在 2.3 GPa 和 5.4 GPa 的压力下，在拉曼光谱中观察到两个相变，这对应于分子间和分子内振动模式的显著变化。在 10.2 GPa 以上，所有的拉曼峰都消失在荧光背景中；然而，在 20.0 GPa 以上进一步压缩时，在 1600、2993 和 3181 cm(-1) 处观察到三个宽峰，表明菲已转变为非晶相。使用 X 射线衍射，从拉曼光谱中观察到的相应相的结构用 P2(1)空间群索引，用于相 I（0-2.2 GPa），P2/m 用于相 II（2.2-5.6 GPa），P2/m+Pmmm 用于相 III（5.6-11.4 GPa），其中存在结构共存，在 11.4 GPa 以上，结构用 Pmmm 空间群索引。尽管菲在 20.0 GPa 以上已转变为氢化非晶碳结构，但根据我们的 X 射线衍射图案，这些非晶团簇仍表现出特征的结晶行为。我们的结果表明，在高压下，菲中存在长程周期性和局部无序状态共存。
