Accurate ab initio determination of magnetic interactions and hopping integrals in La2-xSrxCuO4 systems

摘要

The nature of magnetic interactions and electron transfer processes in La22xSrxCuO4 systems arestudied, by means of an ab initio embedded cluster model approach, using a difference dedicatedconfiguration interaction ~DDCI! procedure. For the undoped system, the crucial role played by theligand to metal charge transfer ~LMCT! configurations in the magnetic process makes necessary theuse of an enlarged DDCI space, which explicitly takes account of the relaxation of these LMCTconfigurations. This procedure allows us to approach the experimental magnetic coupling constantvalue. In hole-doped systems, the value obtained for the electron transfer integral, t, is of 0.54–0.57eV. The extra hole, characterized from the nature and occupation of differential natural orbitals,has a strong p character ~approximately 50%! and is essentially localized in CuO2 planes. Theseresults are in agreement with the experimental evidence about these kinds of compounds. Neitherthe value of t nor the nature of the extra hole are seriously affected by the optimization of theorbitals used in the CI expansion. This suggests that a t – J effective Hamiltonian is an adequatemodel to study the electronic properties of these systems