DENSITY FUNCTIONAL APPROXIMATION FOR THE KINETIC-ENERGY OF INDEPENDENT ELECTRONS IN ONE DIMENSION

We present an explicit approximation for the kinetic energy of independent electrons in one dimension, based on the averaged-density approximation. This non-local approximation is compared with the gradient expansion and the exact results for a series of characteristic problems, to establish their relative accuracy. Unlike other previous studies we have carried out the full minimization of the energy, instead of the simple evaluation of the kinetic energy with the exact density distribution, which leads to inaccurate valuations of the approximations.