First-principles band-structure calculations as a tool for the quantitative interpretation of Raman spectra of high temperature superconductors

We have performed first-principles band structure calculations in order to investigate vibronic and optical properties of YBa(2)Cu(3)O(7). A formalism describing temperature dependent Raman spectra from such ab-initio results has been applied to the 500 cm(-1) apex oxygen mode and its overtone in good agreement with experimental results. The dynamical matrix of the five A(1g) modes established by atomic-force calculations is studied in detail showing rather good agreement with experimental eigenfrequencies and normal coordinates. The effect of isotope substitutions on the phonon frequencies is investigated. We demonstrate that the calculated vibronic properties of high T(c) materials are improved by applying a generalized gradient correction scheme for the treatment of exchange and correlation effects instead of the local-density approximation.