On the local intermolecular ordering and dynamics of liquid chloroform

Abstract

Recently published neutron scattering experiments suggest local molecular ‘polar stacking’ in bulk liquid chloroform. We present molecular dynamics simulations of liquid chloroform that confirm the existence of these structures in relative populations that agree with experiment. Removing the electrostatic contributions to the chloroform force field leaves these structures mostly unchanged. Dynamic studies show that the lifetimes of these short-lived structures are also unchanged when disabling electrostatics. This set of results confirms that these polar-stacked structures are the result of geometrical packing, as opposed to dipole-dipole interactions or other electrostatic driving forces. We also extend this investigation of local intermolecular ordering in chloroform to relate these polar stacking populations to the well-known ‘Apollo configuration,’ where nearby molecules have collinear, head-to tail-dipole moment vectors. We find that the ‘Apollo configuration’ represents only a very small fraction of the total population in bulk liquid CHCl3.