The reaction energies and reaction barriers for a subset of pathways were recalculated on a amorphous silica slab model with a large unit cell (21.6 Å× 21.6 Å× 34.5 Å) and compared with cluster model results for validation. These calculations were performed on the amorphous structure reported by Floryan, generated from an annealing process using classical molecular dynamics and multiple dehydration processes, which results in siloxane rings with different sizes. The Ga-ethyl moiety was created using the same approach as was employed in cluster models. Previous studies indicate that the less-constrained, three-coordinated Ga sites are responsible for the oligomerization chemistry, whereas the constrained four-coordinated sites are relatively inactive due to steric hindrance effects. Therefore, the periodic slab calculations focused on the less-constrained Ga site.