Statistical Mechanics of segregation in binary granular mixtures
  We discuss mixing/segregation phenomena in a schematic hard spheres lattice model for binary mixtures of granular media, by analytical evaluation, within Bethe-Peierls approximation, of Edwards' partition function. The presence of fluid-crystal phase transitions in the system drives segregation as a form of phase separation. Within a pure phase, gravity can also induce a kind of vertical segregation not associated to phase transitions. 
M. Tarzia, A. Fierro, M. Nicodemi, M. Pica Ciamarra, A. Coniglio