"Radiation induced swelling in Titanate Pyrochlore oxides" - Ion irradiation experiments and atomistic simulations were used to demonstrate that irradiation-induced lattice swelling in the complex oxides, Lu2Ti2O7 (LTO), Er2Ti2O7 (ETO), and Y2Ti2O7 (YTO), is due primarily to the formation of cation antisite defects. Polycrystalline LTO, ETO, and YTO samples were irradiated with 400 keV Ne++ ions at cryogenic temperature to very low displacement damage doses (well below the threshold for amorphization). X-ray diffraction (XRD) revealed that in the ion irradiated LTO samples (for instance), cation antisite formation correlates directly with lattice swelling and indicates that the volume per antisite pair is approximately 12 3. First principles calculations confirmed that lattice swelling is best explained by antisite defects. In particular, calculated cation antisite pair formation volumes in LTO are 16.9 3 (large separation between antisites) and 19.7 3 (nearest neighbor antisite configuration), compared to much larger calculated cation Frenkel defect formation volumes of 49.7 3 and 53.5 3, for Lu and Ti Frenkel pairs, respectively. Temperature accelerated dynamics (TAD) simulations indicate that cation Frenkel defects in LTO are metastable and decay to form neighboring antisite defects. These results are evaluated in the context of the role of lattice disorder on the radiation tolerance (or conversely, the radiation susceptibility) of complex oxide ceramics.