Assessment of dispersion correction methods within density functional theory for energetic materials

Abstract

Accurate description of the non-covalent intermolecular interaction is significant for the study of energetic materials. Here, the performance of a variety of dispersion correction methods within density functional theory (DFT) is assessed carefully for six energetic molecular crystals using experimental data as benchmark. We consider semi-empirical DFT plus dispersion correction methods (DFT-D, including DFT-D2 and DFT-D3) and non-empirical van der Waals density functional correction methods (including vdW-DF, vdW-DF2, optPBE-vdW, optB88-vdW and optB86b-vdW). The calculative cell volume, lattice energies, pressure-induced change of volume and bulk modulus are compared with the available experimental data. At ambient condition, theoretical cell volumes by optPBE-vdW, PBE-D3 and vdW-DF2 are in reasonable accordance with experimental data, while PBE-D3 and vdW-DF2 give satisfactory for lattice energies. Under high pressure, both semi-empirical PBE-D3 and non-empirical vdW-DF2 methods could yield reliable results, in which the results by PBE-D3 have smaller deviation from experiment than vdW-DF2 in the entire pressure range. Furthermore, bulk modulus by PBE-D3 calculations also compares reasonably with experimental data. These present assessments provide valuable guidelines for selecting the appropriate method to investigate physical and chemical proprieties of energetic materials in the future.

Keywords:

• Energetic materials
• dispersion correction
• lattice energy
• bulk modulus
• assessment