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 Lu 3+ to La 3+ on the A site and from Ti 4+ to Ce 4+ 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.