High pressure Raman spectroscopic study of structural polymorphismin cyclohexane

Abstract

We have performed a Raman spectroscopic study of cyclohexane at high pressures up to 40GPa at ambient temperature and present evidence for one or two new phases of cyclohexane which appear around 10 and between 25 and 37GPa. The R1 and R2 lines of a ruby in the cyclohexane sample were well-resolved to our highest pressure, and the sample was highly transparent. Because cyclohexane is nonpolar, relatively inert, and a liquid at room temperature, it is an excellent and easy-to-use pressure medium, especially for reactive materials. At 40GPa, we heated the sample to 200 °C for several hours and then performed Raman measurements while decreasing pressure at ambient temperature. The material remained in its original liquid form demonstrating that the molecule is remarkably resilient.