SPIN BAGS, POLARONS, AND IMPURITY POTENTIALS IN LA2-XSRXCUO4 FROM 1ST PRINCIPLES

A full-potential version of a recently proposed generalization of the local-density method (LDA + U) is used to study the influence of impurities, lattice, and magnetic relaxation in La2-xSrxCuO4. The carriers form mean-field analogs of Zhang-Rice singlets, which are only slightly affected by impurity and in-plane lattice relaxation effects. On the other hand, an "anti-Jahn-Teller" polaron, characterized by a 0.26 angstrom shorter Cu to apical-oxygen bond length and triplet spin, is nearly stable. Although the impurity potentials are similar, the self-localization effects are much stronger in La2-xSrxNiO4.