Non-orthogonal orbitals for localized electrons III. Application to periodic one dimensional lattices

A new hybrid method associating an effective spin hamiltonian with an approximate spin function is applied to an infinite s = 1/2 magnetic chain. The effective spin hamiltonian is derived from the single configuration spin-coupled valence bond wave function built upon weakly overlapping non-orthogonal orbitals. The approximate spin function gives a zeroth order description of the short range spin correlation while insuring a proper translational symmetry. The variationally optimized magnetic coupling integrals are extracted using the long range Pariser-Parr-Pople model and the influence of the exchange and Coulomb interactions cut off is shown. (C) 2001 Published by Elsevier Science B.V.