In GAFF, the angle bending, bond stretching bonded interactions are modelled using a harmonic potential making it non-reactive thus greatly simplifying the parameterization process. The torsional potential is expressed as a Fourier series. For non-bonded interactions, the van der Waals (vdW) interactions are described by a 12-6 Lennard Jones potential and electrostatic interactions are modeled using atom-centered fixed charges.