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