The bulk crystal was energy-minimized and slowly thermalized to 300 K under 3D periodic boundary conditions (PBCs), using a Langevin thermostat. Subsequently, the PBCs were removed from the z-direction to create a 2D periodic slab. The system was rethermalized at 300 K and then equilibrated for 0.5 ps to allow slab relaxation and stabilization. Three identical W slabs were irradiated sequentially and cumulatively by 4500 incident oxygen atoms each, with incident energies 1, 10, or 30 eV, respectively, randomly choosing a point of impact. The impact energies were selected to explore the effects of oxide creation with low-and high-energy oxygen coming from the plasma. The energies of the oxygen atoms were below the physical sputtering threshold of ~ 40 eV for W by O . The O atoms were placed in the negative z direction, perpendicular to the top surface of the W slabs every 4 ps for incident energies of 10 and 30 eV and every 3 ps for 1 eV, as shown in the initial setup of the system, Figs. ) and (3-a'). A buffer zone of 5 Å was maintained in the x and y directions of the top surface to avoid overlap of periodic border interactions, resulting in an active deposition area of 23×23= 529 Å 2 .