Elastic constants of the metastable orientationally disordered phase Ia of CCl4 by Brillouin spectroscopy

Abstract

The technique of Brillouin spectroscopy has been used to determine the adiabatic elastic constants, including their temperature dependence, and the elasto-optic coefficient ratios of single crystals of the metastable orientationally disordered phase Ia of CCl4. The values of the elastic constants at 244.1 K are C11=35.7, C12=31.6, and C44=11.1 (in units of kbar) and the elasto-optic coefficient ratios are P12/P11=0.85 and P44/P11=0.22. The elastic constants results suggest that there is strong rotation–translation coupling in the k=0 acoustic wave vector regime and that this coupling is likely responsible for the metastability of the fcc phase Ia with respect to the rhombohedral phase Ib.