Molecular dynamics study of defect in amorphous silica; generation and migration

Fused silica is a material of interest due to its increasing number of applications in many different technology fields. In thermonuclear fusion it is one of candidate materials for both final focusing optics of lasers for NIF and future inertial fusion reactors and diagnostics of the Safety and Control Systems of the ITER machine as well as DEMO magnetic fusion reactors. In operation, these materials will be exposed to high neutron irradiation fluxes and it can result in point defect. Materials properties of interest (optical absorption, radioluminescence, mechanical properties,...) are closely related to the presence of defects. These defects can be generated directly by irradiation or by the presence of impurities in the material. We present molecular dynamic simulation of displacement cascade due to energetic recoils in amorphous silica without hydrogen atoms and with 1% of hydrogen atoms trying to identify defects formation and we present molecular dynamics simulations to study the effects of hydrogen atoms in this material and their interaction with defects; The diffusion coefficients and mechanisms of H mobility in fused silica has been calculated and compared with those existing in the literature. The interatomic potential developed by Feuston and Garofallini has been used in both studies