Predicting lattice energy and structure of molecular crystals by first-principles method: Role of dispersive interactions

Abstract

The accurate calculation of lattice energy and structure of molecular crystals represent a test of the ability of first-principles periodic density functional method to model the relatively weak intermolecular interactions found in molecular crystals. The weak intermolecular dispersion interactions need to be considered for the accurate prediction of crystal structure and lattice energy of molecular crystals. In this paper, we report the calculation of lattice energies and structure of a set of eight molecular crystals at the ab initio level of theory. Hartree–Fock and density functional theory with and without dispersion correction potential were employed. Our results clearly show with application of triple zeta polarization (TZP) basis set, the lattice parameters obtained using B3LYP functional with dispersion interactions give better agreement with the experimental results. On the other hand, the lattice energies obtained using B3LYP-D/TZP method is severely underestimated. The lattice energies calculated at B3LYP-D/6-31G(d,p) level of theory are in close agreement with the corresponding experimental results because of smaller size of basis sets provide large basis set superposition errors which compensate the missing dispersion energies.