Generation and solution of effective many-body Hamiltonians for rare earth and transition metal compounds

摘要

This paper gives an overview of the local density approximate (LDA) generation of effective Hamiltonians for a series of d and f electron Mott insulators and reviews their approximate solution for periodic clusters. The (charge-transfer insulator) materials considered are CeO(sub 2) and PrO(sub 2), the high-(Tc) parent La(sub 2)CuO(sub 4), and three isostructural compounds, K(sub 2)CuF(sub 4), K(sub 2)NiF(sub 4), and La(sub 2)NiO(sub 4). This paper first introduces the effective Hamiltonains in stages by considering first the Coulomb operator for a single atom or ion, and then introduces the additional hopping parameters required for a collection of atoms. Then an improved treatment of screening effects is considered, noting that Hartree-Fock calculations with screened interactions provide approximately correct insulating gaps for charge-transfer insulators. Essential spin correlations and their impact on quasiparticle dispersion are discussed, based on configuration interaction calculations for clusters. The range of validity of the present effective Hamiltonians is discussed. Conclusions are offered. 64 refs, 4 figs, 3 tabs.