  Based on the calculation of the quasiequilibrium statistical sum by means of
the functional integration method, we obtained a nonequilibrium statistical
operator for the electron subsystem of a semibounded metal in the framework of
the generalized jellium model in the Gaussian and higher approximations with
respect to the dynamic electron correlations. This approach allows one to go
beyond the linear approximation with respect to the gradient of the
electrochemical potential corresponding to weakly nonequilibrium processes and
to obtain generalized transport equations that describe nonlinear processes.
