  Thermodynamics of a pseudospin-electron model without correlations is
investigated. The correlation functions, the mean values of pseudospin and
particle number, as well as the thermodynamic potential are calculated. The
calculation is performed by a diagrammatic method in the mean field
approximation. Single-particle Green functions are taken in the Hubbard-I
approximation. The numerical research shows that an interaction between the
electron and pseudospin subsystems leads in the $\mu={}$const regime to the
possibility of the first order phase transition at the temperature change with
the jump of the pseudospin mean value $<S^z>$ and reconstruction of the
electron spectrum. In the regime $n={}$const, an instability with respect to
phase separation in the electron subsystem can take place for certain values of
the model parameters.
