A partitioned density functional theory of freezing: Application to soft spheres

A non-perturbative density functional theory (DFT) for inhomogeneous fluids is developed by partitioning the functional into short range ('entropic') and long range ('energetic') contributions. The short range part is treated using standard weighted density functional techniques and the long range contribution is evaluated exactly. This method, which is a generalization of a method due to Likes, C., and Senatore, G., 1995, J. Phys.: Condens. Matter, 7, 6797, does not require the use of a reference system. Results are presented for the calculation of the crystal/fluid phase coexistence for systems interacting with inverse-power potentials of the form r(-n), where n = 4, 6 and 12. These results show that this non-perturbative DFT is capable of predicting the freezing of long range inverse power systems (n = 4, 6) into a body-centred-cubic lattice. Improvements over earlier methods also are noted in the current results for the solid structure as measured by the Lindemann ratio.