99-07U

Equilibrium states of a pseudospin-electron model with interaction of antiferroelectric type between pseudospins are studied. Calculations of the pseudospin oder parameters, themodynamic potential and free energy are performed. An analysis of phase transitions in the system is made in too different regimes: at constant values of chemical potential (transitions with jump-like chages of mean values of pseudospins) and at constant mean electron concentration (separation into phases with different concentrations and valuses of the oder parameters).