Premelting structure: Vibrational dynamics of liquid, undercooled liquid, glassy, and crystal states in methylcyclohexane and deuterated methylcyclohexane

摘要

We present the results of the Raman studies on vibrational dynamics and static properties of methylcyclohexane (MCH) and deuterated methylcyclohexane (MCH-d_(14)) in distinct thermodynamic states ranging from normal liquid, undercooled liquid to crystal and glassy states. We have studied the low frequency Raman spectra in the range of 15-200 cm~(-1) and the CH_2 rocking mode of MCH and MCH-d_(14) as a function of cooling and warming rates and temperature in the range of 10-293 K. We have identified the premelting crystal structure (crystal beta) of MCH in the temperature range of 140-147 K that proceed the melting both for the glassy state and the equilibrium crystal state (crystal alpha) of MCH. Deuterated MCH exists only in one crystal form (crystal beta) within the studied temperature range.