Zaanen J., Jepsen O., Gunnarsson O., Paxton A.T., Andersen O.K., Svane A.
The significance of local density band structure results for high Tc compounds is critically discussed. It is pointed out that straightforward application of this method can be misleading because of the correlated nature of these materials. However, with LDA numbers can be derived for the parameters appearing in the models in which correlation is treated explicitly. The authors arrive at the conclusion that despite a large U the high Tc materials should be viewed as itinerant materials. Turning to ground state properties, they show that the LDA fails to describe the antiferromagnetism of La2CuO4 and it is pointed out that this may be cured by the inclusion of self interaction corrections. Finally, using a proposed oxygen defect structure for YBa2Cu3O7-x and a simple tight binding model based on band structure calculations, they show that jumps and plateaux in the hole counts in the planes and chains occur as a function of x. These features are perfectly correlated with the occurrence of the antiferromagnetic, as well as of the 60 K and 90 K superconducting phases.
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