HIGH-ORDER PERTURBATION ENERGY OF METAL ELECTRONS IN AN EXTERNAL ELECTRIC-FIELD

Energy of the electron gas perturbed by a constant electric field is e xamined to the eighth order of the Rayleigh-Schrodinger perturbation s eries. The method of the calculation is based on the local density app roach to the non-interacting many-electron system in which the electro n wavefunctions are represented by the standing-like waves. The conver gence of the series depends on the strength of the electric held, the radius of the metal sample and the quantum number defining the electro n energy. For the case of convergence a decisive contribution to the p erturbation energy is obtained from the second-order term. This term g ives the electric polarizability to be only slightly different from th at obtained in the former theories. For the sake of comparison the hig h-order perturbation calculation done for a three-dimensional electron gas is repeated also for the case of the one- and two-dimensional ele ctron gas systems having a finite size.