Electronic and vibrational properties of the high <i>T</i> _c superconductor Bi ₂ Sr ₂ CaCu ₂ O ₈ : an <i>ab initio</i> study

Abstract

Abstract In this work, ab initio calculations were performed in order to study the vibrational spectra of the Bi 2 Sr 2 CaCu 2 O 8 (Bi2212) compound. A structural modulation correction on some atomic positions, producing a distorted structure with lower symmetry, is used for the calculation. We argue that this correction allows to account for an average effect of the incommensurate superstructure, generating a more accurate representation of the real unit cell observed in this compound. A complete and conclusive vibrational assignment is performed, discussing the correspondences with previous experimental and theoretical reports. A brief analysis of the electronic density of states and band structure comparing the tetragonal and distorted unit cell is also included.