High-Pressure Studies of Cyclohexane to 40 GPa

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• 作者：Michael Pravica ; Yongrong Shen ; Zachary Quine ; Edward Romano ; David Hartnett
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：April 26, 2007
• 年：2007
• 卷：111
• 期：16
• 页码：4103 - 4108
• 全文大小：334K
• 年卷期：v.111,no.16(April 26, 2007)
• ISSN：1520-5207

文摘

We present data from two room temperature synchrotron X-ray powder diffraction studies of cyclohexane upto ~40 and ~20 GPa. In the first experiment, pressure cycling was employed wherein pressure was variedup to ~16 GPa, reduced to 3.5 GPa, and then raised again to 40 GPa. Initially, the sample was found to bein the monoclinic phase (P12₁/n1) at ~8.4 GPa. Beyond this pressure, the sample adopted triclinic unit cellsymmetry (P1) which remained so even when the pressure was reduced to 3.5 GPa, indicating significanthysteresis and metastability. In the second experiment, pressure was more slowly varied, and the monoclinicunit cell structure (P12₁/n1) was observed at lower pressures up to ~7 GPa, above which a phase transformationinto the P1 triclinic unit cell symmetry occurred. Thus, the pressure onset of the triclinic phase may bedependent upon the pressurizing conditions. High-pressure Raman data that further emphasize a phase transition(probably into phase VI) around 10 GPa are also presented. We also have further evidence for a phase VII,which is probably triclinic.