Theoretical Approach to the Correlations of a Hard-Sphere Crystal
  We present the first theoretical approach to the angular-average of the two-body correlation function $\tilde g(r)$ for simple solids. It is based on three sum rules for $\tilde g(r)$: the compressibility and virial equations and the normalization. We apply the theory to determine this correlation function for the case of the FCC solid phase of hard spheres. The agreement with simulation data is excellent over all the density range. The application to other simple systems is discussed. The approach opens a new route to perturbation theories for simple solids. 
C.Rascon, L.Mederos and G.Navascues (Universidad Autonoma de Madrid /   Instituto de Ciencia de Materiales-CSIC)