Assessing the Performances of Dispersion-Corrected Density Functional Methods for Predicting the Crystallographic Properties of High Nitrogen Energetic Salts

Several density functional methods with corrections for long-range dispersion interactions are evaluated for their capabilities to describe the crystallographic lattice properties of a set of 26 high nitrogen-content salts relevant for energetic materials applications. Computations were done using methods that ranged from adding atomatom dispersion corrections with environment-independent and environment-dependent coefficients, to methods that incorporate dispersion effects via dispersion-corrected atom-centered potentials (DCACP), to methods that include nonlocal corrections. Among the functionals tested, the most successful is the nonlocal optPBE-vdW functional of Klimes and Michaelides that predicts unit cell volumes for all crystals of the reference set within the target error range of +/- 3% and gives individual lattice parameters with a mean average percent error of less than 0.81%. The DCACP, Grimmes D3, and Becke and Johnsons exchange-hole (XDM) methods, when used with the BLYP, PBE, and B86b functionals, respectively, are also quite successful at predicting the lattice parameters of the test set.