COMPUTATIONS OF POINT-DEFECT ENERGIES IN YBA2CU3O6.5

The atomistic simulation technique has been employed to compute point defect energies in YBa2Cu3O6.5. Potentials employed earlier for YBa2Cu3O7 and more recent modifications are employed. The dominant oxygen ion defect is predicted to be of the Frenkel type in comparison to Schottky types. This result is similar to previous behavior found in YBa2Cu3O7 and YBa2Cu4O8. Point defects involving cations are predicted to be less likely except for Cu+ that can form at an interstitial site in the Y plane. The potentials are used to demonstrate a dependence of internal bond lengths upon copper-oxygen hole concentration which is similar to experimental determinations. Realistic values for the energy of oxygen intercalation are derived with these potentials.