Quantitative aspects of the dynamical impurity approach

A calculation technique in the context of the self-energy functional approach (SFA) and its local form, the dynamical impurity approach (DIA), will be proposed. This technique allows for a precise calculation of the derivatives of the grand potential functional used in the search for a stationary point. To make a closer comparison of the DIA with the dynamical mean-field theory (DMFT), and to demonstrate the proposed technique, we calculated paramagnetic U-T phase diagram of the Hubbard model at half-filling, which exhibits metal-insulator transition.