First principles study of the normal state electronic properties of the Bi-2212 cuprate superconductor

We present detailed first-principles calculations of the normal state electronic properties of the Bi2Sr2CaCu2O8 (Bi-2212) high T-C superconductor by means of the linearized augmented plane wave (LAPW) method within the framework of density functional theory (DFT). We describe the crystal structure by the body-centered tetragonal (BCT) cell with space group I4/mmm and optimize its volume, c/a ratio and atomic positions by total energy and atomic-force minimization. The optimization of the cell leads to small but visible changes in the topology of the Fermi surface, rounding the shape of the CuO2 barrels, and moving both the BiO bands, responsible for the pockets near the (M) over bar point, below the Fermi level. We have then studied the influence of the large distortions in the BiO plane observed in nature by means of an root2 x root2 orthorhombic cell (with Bbmb space group). Differently to what has been observed in the literature for the Bi-2201 compound, we find that for Bi-2212 the orthorhombic distortion does not induce relevant changes to the binding energies of the BiO bands, conserving their metallic character. (C) 2003 Elsevier B.V. All rights reserved.