Atomistic simulations of radiation-induced defect formation in spinels:: MgAl2O4, MgGa2O4, and MgIn2O4

Molecular dynamics simulations of collision cascades were performed in three spinel oxides with varying inversion, namely normal magnesium aluminate, MgAl2O4, half-inverse magnesium gallate, MgGa2O4, and inverse magnesium indate, MgIn2O4. The response of each of these oxides for energies of up to 10 keV for the initial knock-on event was analyzed and compared. Defect production was characterized mainly by split interstitials/crowdions and cation antisite or disorder defects. The results show that cation interstitials preferentially occupy octahedral sites in all three materials. In the normal spinel, subcascade branching occurs and the defects at the end of the cascade are generally isolated, whereas in the half-inverse spinel, the higher energy cascades show a core damage region some of which consists of a partial rearrangement of atoms to the normal spinel structure and a partial transformation to a disordered rocksalt structure. In the fully inverse spinel a more connected region of the disordered rocksalt structure with the cascade core is evident.