  We present an efficient impurity solver for the dynamical mean-field theory
(DMFT). It is based on the separation of bath degrees of freedom into the low
energy and the high energy parts. The former is solved exactly using exact
diagonalization and the latter is treated approximately using Green's function
equation of motion decoupling approximation. The two parts are combined
coherently under the standard basis operator formalism. The impurity solver is
applied to the Anderson impurity model and, combined with DMFT, to the one-band
Hubbard model. Qualitative agreement is found with other well established
methods. Some promising features and possible improvements of the present
solver are discussed.
