Simulations of cascades in pure and alumina doped magnesia

Atomic scale molecular dynamics simulations of displacement cascades are carried out in an initially defect-free MgO lattice and in a lattice where 0.2% of the Mg2+ ions have been replaced by Al3+ ions, charge compensated by magnesium vacancies. Results show that the properties of the cascade in the perfect lattice exhibit considerable anisotropy with respect to the direction of the incident primary knock-on atom (PKA). We find that a different anisotropy of equivalent magnitude occurs as a consequence of the (random) distribution of defects in the vicinity of the cascade. This suggests that the details of damage production during a cascade event can depend sensitively on the distribution of dopants and impurity atoms around the PKA.