Over more than 50 years a wide variety of force field models have been developed to calculate interaction energies between molecules without the need of performing computationally more demanding quantum chemical (ab initio, DFT or semi-empirical) calculations which aim to find approximate solutions to the many-body Schrödinger equation. For so-called non-reactive systems, these force fields often come in the form of four components: 1) a sum of harmonic oscillator terms for describing stretching and/or contractions of the bonds of a molecule, 2) a sum of harmonic oscillator terms to describe bending of the bonds, 3) a sum to describe rotations of the dihedral angles of a molecule. 4) at last, a sum of Coulomb energies and other long-range interactions, often expressed as a combination of partial charges and a Lennard-Jones styled potential between all pair of atoms belonging to atoms that do not share one of the terms mentioned in 1-3, either in the same or in different molecules.