Lattice Model for Metal Ammonia Solutions

We study metal ammonia solutions using a generalized Kimball-Falicov model. The lattice model contains a fluid-fluid interaction term and an electron-fluid interaction with a hard core and an attractive tail. We derive the phase diagram using a strong-coupling mean field theory based on the slave boson approach to the Hubbard model. The attractive force favors the homogeneous phase and a regime where electrons localize in cavities devoid of fluid particles over phase separation. The Gaussian fluctuations suggest the existence of bicontinuous channels percolating through the system. Comparisons with experiments and computer simulations are presented.