Pressure-induced structural phase transition of CCl4

Calculation of thermodynamic quantities for carbon tetrachloride (CCl4) close to the III–IV phase transition

“…Under the compression of 0.13 GPa, at room temperature (300 K), the liquid phase solidifies to the phase I, which is transformed into the phase II at 0.4 GPa and into the phase III at 0.7 GPa with a monoclinic structure. At a higher pressure of above 2 GPa at 520 K, III-IV phase transition occurs [3], as also observed by Raman spectroscopy [5,6].…”

“…We analyzed here the observed volume data [6] at various pressures close to the III-IV transition in CCl 4 according to…”

“…The solid phase III is stable under pressure, which is a highly birefringent phase, whereas a nonbirefringent phase IV has a highly symmetric structure [3]. It has been reported that the crystal structure of phase IV has not been determined yet [6]. The solid phases of I, II and III, and the liquid phase (L) have been obtained experimentally in the T-P phase diagram [2], as also given in Fig.…”

“…Dual melting curves for the I a -liquid and I b -liquid, and also curve for the II-I b transition have been determined in the experimental T-P phase diagram [13]. An experimental V-P phase diagram showing the solid phases III and IV in CCl 4 has been given in a previous study [6].…”

“…Differential thermal analysis (DTA) [7,11,14], calorimetry [8][9][10]15], X-ray diffraction [1][2][3], birefringence [16], Raman [6,17] and Brillouin scattering [18,19] have been used to investigate experimentally the phase transition in CCl 4 . It has been observed that CCl 4 like some other molecular crystals exhibits a second-order phase transformation prior to melting [20].…”