where N cos i is the user-selected number of cosine functions employed to model dihedral δ i , while k f t i j , n i j and γ i j are respectively the force constant, multiplicity and phase of the j th term of the series. Finally, since the MD runs are expected to explore a large portion of the PES, in which the target molecule might be in different conformations, intramolecular non-bonded interactions may be introduced between selected atom pairs. This is necessary for instance to account for the steric repulsion between close atoms or the possible intramolecular hydrogen bonds (HBs). Such interactions can be introduced through specific LJ intramolecular model functions, depending on soft intramolecular distances (r so f t ):