For a more comprehensive analysis, we divided the W slab into bins in the negative z direction, each containing roughly 200 oxygen deposits (equivalent to approximately 3 to 3.5 bin thickness). To understand the dynamics of O accumulation, we studied the nO/nW ratio along the thickness of the slab + ad layer, shown in Figure . Bins of 200 atoms, as previously illustrated in Figure S-2, were utilized. We found that the nO/nW ratios for the 1, 10 and 30 eV cases were larger than 3 in the higher top of the ad layers, indicating a high buildup of O on the surface of W at the beginning of the accumulation process. However, in the B-A-B region, the ratio was 1.7:1. We also observed an increase in the nO/nW ratio throughout the W and ad-layers as a function of the z coordinate. This ratio reaches 3 at the upper part of the ad layers, typical for WO3. The B-A-B regions exhibit lower nO/nW ratios. The higher bins (Bin 5 for 30eV, Bin 4 for 10eV, and Bin 3 for 1eV in Fig. ) exhibit the highest nO/nW ratios compared to the lower bins. Within the ad layer, as we get closer to the original surface, this ratio decreases, but for all ad layer bins, the ratio is always ≥ 3:1. Detailed results are illustrated in Table -1 of SM and Fig. . Additionally, the nO/nW ratio on the B-A-B layer decreases to 2:1 in the bins close to the original top surface of W and decreases further as we go deeper into the bulk of W. Obtaining nO/nW ratios of ~2 near the bulk W and ~3 in the ad layers aligns well with the existing literature . Oxygen atoms move downward while W atoms migrate to higher ad layers until the ratio of the top layers turns to be ~3:1. The process of O deposition on W involves a series of sequential substeps, as reported in the literature . Initially, O impacts at 1 eV lack the penetrative power to overcome the surface barrier of W. However, the adsorbed oxygens bond to the top layer of W and amorphize it, changing the surface potential barrier, and thus opening the doors for incoming oxygen atoms to penetrate below the original W surface, as seen in Fig. . It is noteworthy that we applied the NVE ensemble constraints to all three O-saturated W systems, 100 picoseconds, to observe the stability of the nO/nW ratios. These ratios remained stable over time. WO3 is recognized as the most stable form of tungsten oxide in the literature ,