Is the Induction Energy Important for Modeling Organic Crystals?

We compare two methods for estimating the induction energy in organic molecular crystals by approximating the charge density polarization in the crystalline state. The first is a distributed atomic polarizability model combined with distributed multipole moments, derived from ab initio monomer properties. The second uses an ab initio calculation of the molecular charge density in a point-charge field. Various parameters of the models, such as the rank of polarizability model, effect of self-consistent iterations, and damping, are investigated. The methods are applied to a range of observed and predicted crystal structures of three particularly challenging molecules, namely oxalyl dihydrazide, 3-azabicyclo[3,3,1]nonane-2,4-dione, and carbamazepine, as well as demonstrating the importance of induction in the naphthalene crystal. The two models agree well considering the different approximations made, and it is shown that the induction energy can be an important discriminator in the relative lattice energies of structures with substantially different hydrogen-bonding motifs.