You got it. The from_arrays is a fairly new feature, strangely. We’ve been accustomed to be mostly from_string. The only thing different you may notice about the molecule you built (compared to psi4.geometry(mol_str) is that the molecule isn’t “activated”, so you’ll have to pass it (e.g., psi4.energy(..., molecule=p4_mol)) rather than having it magically plucked from the environment.