Configuration interaction method for model Hamiltonian clusters

Abstract

Ground state energies of the Hubbard-Hamiltonian defined on small clusters have been obtained using configuration interaction like methods. It is shown that it is convenient to choose between a single-particle-energy basis and the site basis depending upon the range of Hubbard U. The method is illustrated on six- to nine-site clusters of ring geometry for a half-filled band. The results indicate that it is possible to pickup about 70 to 80% of the ground state energy for appropriate ranges of the Hubbard U parameter with reduced number of multiparticle basis states.