Density functional for hard sphere crystals: A fundamental measure approach

A new free energy density functional for hard spheres is presented, along the lines of the fundamental measure theory, which reproduces the Percus-Yevick equation of state and direct correlation function for the fluid, with a tensor weighted density. The functional, based on the zero-dimension limit, is exact fur any one-dimensional density distribution of the spheres. The application to the hard sphere crystals fives excellent results, solving all of the qualitative problems of previous density functional approximations, including the unit cell anisotropy in the fee lattice and the description of the metastable bce lattice.