Experimental assessment of the extent of orientational short-range order in liquids

The spatial extent of orientational short-range order in liquid and rotationally disordered phases of two halogen-substituted methanes are examined by means of neutron diffraction. The pair distribution functions measured within the liquids are compared to those corresponding to the rotator-phase crytals where the separation between orientational and positional correlations is enabled by the presence of time-averaged fcc lattices. The two condensed systems under scrutiny comprise a material devoid CCl4 and another C CD3 3Cl having a relatively strong molecular dipole moment. Our results show orientational correlations to be confined below the second coordination sphere. Furthermore, contrary to what could be expected, angular correlations within the nonpolar material are of comparable strength to those present within the polar C CD3 3Cl.