However if the degree of either internal bond carbons is greater than 2, then the internal x-y bond is the rotational axis for more than one dihedral angle (with up to 9 dihedral angles contributing to the conformational PEL depending on the C-atom degrees). In such cases, the contributions of all dihedral angles can be simplified by considering the angle bisector of the leaf carbons on each side of the shared bond. One approach is to let θ be a 3-body equilibrium angle going from one leaf Catom to the C-atom of the internal bond and to the next leaf C-atom (Table ). Now define an angle bisector in the plane of the three C-atoms as ψ = θ /2. Two terms now contribute to the component function as f (φ ± ψ). When x > 2 or y > 2, a building block function g 1-x-y-1 (φ ) may be calculated over multiple component functions using the angle bisector(s). If there are i angle bisectors present in the molecular sub-unit for the branched alkane, the building block function is