Spontaneous cationic Frenkel pair recombinations in lanthanum pyrozirconate (La2Zr2O7)

Spontaneous cationic Frenkel pair recombinations in lanthanum zirconate (La2Zr2O7) pyrochlore are studied with empirical potential molecular dynamics. A complex behavior is observed depending on the distance between the vacancy and the interstitial and on the nature of the cations lying in between them. While interstitials of the first shell near a vacancy readily recombine, interstitials of the second shell never do. The third shell interstitials recombine in half the configurations, i.e. when the intermediate cation is lanthanum, leading to antisites when a zirconium defect pair is considered. The behavior is globally the same in the corresponding disordered fluorite structure, but we observed that in this structure, the number of spontaneous recombinations increases with temperature.