Periodic DFT single-point energy calculations were performed on the force field optimized crystal structures with both the VASP 51-54 code, using plane-wave (PW) basis sets, and CRYS-TAL17 55 using Gaussian Type Orbital (GTO) basis sets. The justification of the choice of basis set is discussed in Section 3.2. Generally speaking, PWs are intrinsically periodic, fast for both energy and its gradient calculations, and the quality of a PW basis set is improvable by a single parameter, namely the electronic kinetic energy cutoff. PW calculations were used for the intermediate level (PBE) energy evaluations. However, due to the extremely high computational costs involved in exact exchange calculations with PW basis sets, the highest level, hybrid functional (PBE0) calculations were perfomed using GTO basis sets. Furthermore, we exploited symmetry in CRYSTAL17, which sped up the PBE0 energy evaluations by a factor of up to the number of equivalent molecules in the unit cell.