The structural second virial coefficient: a spherical-core pair-potential for sulphur hexafluoride

Neutron diffraction data for sulphur hexafluoride gas is reanalysed following the same procedure described in our previous paper but using a spherical-core potential which was not considered in that report. The new spherical-core potential, with parameters epsilon/Ksub(B)K = 405, delta/A = 5.042 and α/A = 0.9225, gives a satisfactory fit to both the virial and structural data. There are now three model potentials, a site-site, a LJ 28-7, and this spherical core which all fit the data very well, indeed the core potential reported here fits rather better than the others. The anisotropic site-site potential is still to be preferred on physical grounds but the new core-potential will be useful where an isotopic potential suffices since it is much simpler to use. (author)