Accurate Lattice Energies for Molecular Crystals from Experimental Crystal Structures

Using four different benchmark sets of molecular crystals, we establish the level of confidence for lattice energies estimated using CE-B3LYP model energies and experimental crystal structures. [IUCrJ 2017, 4, 575-587.] We conclude that they compare very well with available benchmark estimates derived from sublimation enthalpies, and in many cases they are comparable with, and sometimes better than, more computationally demanding approaches, such as those based on periodic DFT plus dispersion methodologies. The performance over the complete set of 110 crystals indicates a mean absolute deviation from benchmark energies of only 6.6 kJ mol-1. Applications to polymorphic crystals and larger molecules are also presented and critically discussed. The results highlight the importance of recognizing the consequences of different sets of crystal/molecule geometries when different methodologies are compared, as well as the need for more extensive benchmark sets of crystal structures and associated lattice energies.