The oxygen positional parameter in pyrochlores and its dependence on disorder

Atomistic simulation calculations based on energy minimization techniques have been used to predict the O positional parameter of a wide range of A₂B₂O₇ pyrochlore oxides. Cations studied range from Lu³⁺ to La³⁺ on the A site and Ti⁴⁺ to Pb⁴⁺ on the B site. In all cases the model included a specific predicted degree of disorder without which it was not possible to reproduce experimental values accurately. However, the extent of disorder invoked was dependent on the specific A and B cations involved, with Gd₂Ti₂O₇ exhibiting the lowest and Gd₂Pb₂O₇ the highest degree of disorder.