Thermodynamics of Pseudospin-Electron Model in the U=0 Limit

Analytical consideration of a pseudospin-electron model in the absence of electron correlations is presented. Pseudospin and electron number mean values, thermodynamic potential, pair correlation functions are obtained in the same self-consistent approximation. The possibility of either first or second order phase transitions between different uniform phases (bistability) as well as between the uniform and the chessboard one is shown. In the regime n=const, an instability with respect to phase separation can take place.