State of the art simulations in electronic structure and total energy for the high temperature superconductor YBa2Cu3O7

We present an ab initio total-energy density functional theory investigations for the stoichiometric high temperature cuprate YBa2Cu3O7 using a FP-LAPW code. Two different schemes, the local density approximation (LDA) and a generalized gradient approximation (GGA) are employed for the treatment of electronic exchange and correlation effects. From theoretical point of view, total-energy calculations and the full-self-consistent energy bands along some high-symmetry points of the Brillouin zone have been carried out. A consistent picture of total and site-projected densities of states, the partial charges and their symmetry-decompositions is as well proposed via calculations. We compare our results to experimental and/or ab initio results, and find that in the case of the LDA, the resulting response show a considerable deviation from experimental values. Invoking GGA, the resulting values are significantly improved in good agreement with experimental findings. On the whole, a consequence of the DFT/LDA-GGA conjecture would be that first-principles calculations based DFT are an appropriate tool in studying such complicated materials as high-temperatures cuprates where the treatment of exchange and correlation effects in an important issue for this task.