Sabharwal Robert J, Huang Yining, Song Yang
Department of Chemistry, The University of Western Ontario, London, Ontario, Canada.
J Phys Chem B. 2007 Jun 28;111(25):7267-73. doi: 10.1021/jp068287v. Epub 2007 May 25.
1,2-Dichloroethane (DCE) was loaded into diamond anvil cells and compressed up to 30 GPa at room temperature. Pressure-induced transformations were probed using Raman spectroscopy. At pressures below 0.6 GPa, fluid DCE exists in two conformations, gauche and trans in equilibrium, which is shifted to gauche on compression. DCE transforms to a solid phase with exclusive trans conformation upon further compression. All the characteristic Raman shifts remain constant in fluid phase and move to higher frequencies in the solid phase with increasing pressure. At about 4-5 GPa, DCE transforms from a possible disordered phase into a crystalline phase as evidenced by the observation of several lattice modes and peak narrowing. At 8-9 GPa, dramatic changes in Raman patterns of DCE were observed. The splitting of the C-C-Cl bending mode at 325 cm-1, together with the observation of inactive internal mode at 684 cm-1 as well as new lattice modes indicates another pressure-induced phase transformation. All Raman modes exhibit significant changes in pressure dependence at the transformation pressure. The new phase remains crystalline, but likely with a lower symmetry. The observed transformations are reversible in the entire pressure region upon decompression.
将1,2 - 二氯乙烷（DCE）装入金刚石对顶砧室，并在室温下压缩至30吉帕。使用拉曼光谱探测压力诱导的转变。在低于0.6吉帕的压力下，液态DCE以两种构象（gauche和反式）处于平衡状态，压缩时平衡向gauche构象移动。进一步压缩时，DCE转变为具有唯一反式构象的固相。所有特征拉曼位移在液相中保持不变，随着压力增加在固相中移向更高频率。在约4 - 5吉帕时，DCE从可能的无序相转变为晶相，这由几个晶格模式的观察和峰变窄所证明。在8 - 9吉帕时，观察到DCE的拉曼图谱发生显著变化。325厘米-1处C - C - Cl弯曲模式的分裂，以及684厘米-1处非活性内模式的观察和新的晶格模式表明又一次压力诱导的相变。在转变压力下，所有拉曼模式在压力依赖性方面都表现出显著变化。新相保持结晶态，但可能具有较低的对称性。在整个压力区域减压时，观察到的转变是可逆的。
