The intermolecular potential of methane A neutron diffraction study on low-density CD4

Abstract Neutron diffraction on low-density systems offers the possibility of a direct probing of the intermolecular forces. This method, used in the last few years for monatomic systems like rare gases, is applied here to the case of gaseous CD 4 at low densities on the 180 K isotherm. The intermolecular scattering has been analysed in order to extract C ( q ), i.e. the Fourier transform of the direct correlation function. The zero-density limit of C ( q ), which depends on the (spherical average of the) pair potential only, is compared to the same quantity obtained from effective intermolecular pair potentials found in the literature.