The ω i and γ 0i angles are important for the structures where H 2 O 2 tends to align parallel to a Nb -O bond, but not when it is parallel to the Nb --O group; in the latter cases, we set ω i = 100 ○ and γ 0i = -90 ○ , which empirically correspond to a "no steric hindrance" configuration. The last two descriptors that we include are the Mulliken charges for Nb and O i (q N b and q O i ) where i = 0, α, β, γ indicates the O center to where H 2 O 2 is initially hydrogen bonded. These charges represent electronic descriptors for the interaction of the H 2 O 2 reactive species with the active site.