Electron correlations in GaAs and AlGaAs superlattices

We have calculated the electronic correlation energy and the exchange energy of a system of GaAs lattice using the density functional theory. In 15 different calculations, we are able to find the energy values for different number of Al and Ga atoms. We have performed the calculation of the energy of the Schroedinger equation in three different approximations, namely, the local density approximation (LDA), the generalized gradient approximation with exchange (GGA-X) and the generalized gradient approximation with exchange and correlations (GGA-XQ. The correlation energy has a peak for the cell which has 9 Ga and 5 Al atoms. In this way, we find that the material for which the composition is in the ratio of GaAl = 9:5, has the strongest electron correlations. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.