For branched alkanes we consider X i = S 1 , indexed by 1 ≤ i ≤ n for n internal bonds, where each circle, S 1 , describes the dihedral angle of four C-atoms. As shown in Figure , observe that the potential energy landscape V : S 1 × S 1 → R for 2-methylpentane is an additive energy landscape V (x 1 , x 2 ) := g 1 (x 1 ) + g 2 (x 2 ) created from the energy functions g 1 : S 1 → R for isopentane (orange slice) and g 2 : S 1 → R for butane (red slice), respectively. When one angle is fixed in Figure , the orange and red slices recover the energy landscapes g 1 : S 1 → R and g 2 : S 1 → R for isopentane and butane, respectively.