Disorder in pyrochlore oxides

Contour plots of disorder reaction energies across a wide variety of A(2)B(2)O(7) pyrochlore oxides have been produced, using atomistic simulation calculations based on energy-minimization techniques. The cations studied range from Lu3+ to La3+ on the A site and from Ti4+ to Ce4+ on the B site. The present results relate the experimentally observed stability range of the pyrochlore structure to A and B cation size and disorder. Disorder enthalpies decrease dramatically with increasing B cation size, while the rate of increase with A cation size depends markedly on the particular B cation. The association of anion Frenkel and cation antisite disorders is found to be of importance.