Unrestricted Hartree-Fock approach to the insulating behavior of antiferromagnetic CaCuO2.

Abstract

Ground-state properties of ${\mathrm{CaCuO}}_{2}$, a parent compound of the high-${\mathit{T}}_{\mathit{c}}$ superconductors, are calcula- ted ab initio using a LAPW spin-unrestricted Hartree-Fock (UHF) scheme. While ${\mathrm{CaCuO}}_{2}$ is a metal within the local-spin density approximation, UHF retains the essential nonlocality of exchange, and predicts a wide gap insulator with an antiferromagnetic moment \ensuremath{\mu}\ensuremath{\approxeq}0.8${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$. Results for hypothetical ferromagnetic ${\mathrm{CaCuO}}_{2}$ indicate that the insulating character does not depend on the magnetic ordering. The shortcomings of UHF are corrected in part with a simple diagonal-screening model.