• sin sr a,pqs 3 κ pq , (4) where p, q enumerate the atoms in the molecule, g pq (s) is the so-called g-function that gives the scattering intensity of the pair of atoms p, q, and r a , l, and κ are the moments of the pair distribution function (PDF) for a given interatomic distance r, and r e is the equilibrium distance for a given atomic pair.