  Systems of charged particles on anisotropic three-dimensional lattices are
investigated theoretically using Debye-Huckel theory. It is found that the
thermodynamics of these systems strongly depends on the degree of anisotropy.
For weakly anisotropic simple cubic lattices, the results indicate the
existence of order-disorder phase transitions and a tricritical point, while
the possibility of low-density gas-liquid coexistence is suppressed. For
strongly anisotropic lattices this picture changes dramatically: the
low-density gas-liquid phase separation reappears and the phase diagram
exhibits critical, tricritical and triple points. For body-centered lattices,
the low-density gas-liquid phase coexistence is suppressed for all degrees of
anisotropy. These results show that the effect of anisotropy in lattice models
of electrolytes amounts to reduction of spatial dimensionality.
