Revised local atomic potential method for predicting properties of energetic materials

Aiming at energetic materials (EMs) consisting of H, C, N, and O, we revised the local atomic potential (LAP) method used in density functional theory (DFT) calculations for describing van der Waals (vdW) interaction. The revised LAPs ensure the 1/r(6) asymptotic behavior of the vdW interaction and smoothly decrease to zero in the core region. The new LAPs are based on the Perdew-Burke-Ernzerhof (PBE) functional. We applied the PBE+LAP method to calculate the densities of 19 representative EMs and compared with the PBE+D method, which is the most widely used method compromising between accuracy and efficiency for including vdW interaction in DFT calculations. The PBE+LAP method achieved mean absolute deviation (MAD) of 0.022 g/cm(3) from experimentally measured densities. In comparison, PBE+D method yielded 0.066 g/cm(3) MAD for the 19 EMs. The PBE+LAP method was also applied to study the polymorphism of six EMs. The results show that in five of them the PBE+LAP method can reproduce the relative stability of different polymorphs according to experiment.