Effects of vacancies on atom displacement threshold energy calculations through Molecular Dynamics Methods in BaTiO3

Abstract A primary approach for evaluating the influence of point defects like vacancies on atom displacement threshold energies values T d in BaTiO 3 is attempted. For this purpose Molecular Dynamics Methods, MD, were applied based on previous T d calculations on an ideal tetragonal crystalline structure. It is an important issue in achieving more realistic simulations of radiation damage effects in BaTiO 3 ceramic materials. It also involves irradiated samples under severe radiation damage effects due to high fluency expositions. In addition to the above mentioned atom displacement events supported by a single primary knock-on atom, PKA, a new mechanism was introduced. It corresponds to the simultaneous excitation of two close primary knock-on atoms in BaTiO 3 , which might take place under a high flux irradiation. Therefore, two different BaTiO 3 T d MD calculation trials were accomplished. Firstly, single PKA excitations in a defective BaTiO 3 tetragonal crystalline structure, consisting in a 2×2×2 BaTiO 3 perovskite like super cell, were considered. It contains vacancies on Ba and O atomic positions under the requirements of electrical charge balance. Alternatively, double PKA excitations in a perfect BaTiO 3 tetragonal unit cell were also simulated. On this basis, the corresponding primary knock-on atom (PKA) defect formation probability functions were calculated at principal crystal directions, and compared with the previous one we calculated and reported at an ideal BaTiO 3 tetrahedral crystal structure. As a general result, a diminution of T d values arises in present calculations in comparison with those calculated for single PKA excitation in an ideal BaTiO 3 crystal structure.