Lowering the symmetry group of carbon tetrachloride by high pressure



Using the pressure-induced polarized Raman spectra of carbon tetrachloride up to 22 GPa, a significant anomalous polarization (the depolarization ratio >0.75) was observed. We analyzed it by evaluating the antisymmetric anisotropy distribution of modes in Td and explored the corresponded molecular structure having been translated from Td into a lower symmetry. The P21/c and Pa3 structures of carbon tetrachloride were optimized as a function of pressure to further confirm that the molecules deviated from regular tetrahedra. The C2v and D2 were analyzed to be candidates of the lower symmetry based on group and Landau theory.