APPLICATION OF THE DENSITY-FUNCTIONAL FORMALISM TO BOUND POLARONS

Calculating the ground state energy of the bound polaron with the help of the density-functional formalism high quality results are found for all alpha and R. Beside the usual energy functional of the electronic density a new energy functional without self-energy contributions can be constructed, allowing to prove quantitatively the applicability of the local density approximation if electron-phonon interaction is included. Furthermore, the validity of the parameterized formula for the exchange-correlation energy of a homogeneous e-h plasma in polar semiconductors is confirmed by the calculations. Comparing both energy functionals new insights are obtained with respect to the structure of these functionals.