APPROACHING PERIODIC-SYSTEMS BY A SELF-CONSISTENT EMBEDDING OF A FINITE CLUSTER

When using a Hamiltonian model, of Hubbard or Heisenberg type, one may approach the properties of a periodic lattice by embedding a finite c luster into a periodic localized function and by self-consistently dre ssing the configuration interaction matrix of the cluster under the ef fect of the charge or spin fluctuations of the neighbor bonds. The eff iciency of the method is illustrated on the 1-D problem, for both Heis enberg and Hubbard Hamiltonians. (C) 1998 Elsevier Science B.V.