Theoretical studies of size effects on surfacial properties for CL-20 and NTO nanoparticles

Abstract

Nanoparticles (NPs) possess the unique physical and chemical properties compared with gas-phase molecule and bulk crystal. Hence, the energetics, electronic structure, and vibrational properties of CL-20 and NTO NPs were investigated by the combinational strategy based on density-functional tight-binding (DFTB) and density-functional theory (DFT) methods. The results show that NPs possess quite different features from the isolated state molecule and the bulk crystal. The excess energies, surface energies, and enthalpy of sublimation for the NPs are predicted. The surface-induced surface states of the CL-20 and NTO NPs result in the significant decrease on the energy gaps and the formation of active sites on the surfaces. The vibrational properties related to the decomposition pathways for both CL-20 and NTO NPs, gas molecules, and bulk crystals are discussed and compared with previous theoretical and experimental values. Our results are expected to provide basic insights into the understandings of the surface effect of nano-sized energetic materials.