Defect formation energies in A2B2O7 pyrochlores

Abstract

We performed ab initio calculations of the cation antisite and anion Frenkel pair defect formation energies for a series of pyrochlores. The obtained energies correlate well with the stability field of pyrochlore. We found that in the compounds that tend to crystallize as a disordered fluorite, the anion Frenkel pair defect formation energy is negative. This correlation suggests that the low energy cost for defect accumulation is one of the driving forces behind the order–disorder transition in pyrochlores