Computational screening of several silicon-based high-energy hexanitrohexaazaisowurtzitane-like derivatives

Silicon-based hexanitrohexaazaisowurtzitane (CL-20) derivatives, including nitro (NO2) and difluoramino (NF2) group containing derivatives, may become important high-energy compounds. Density Functional Theory Becke exchange plus Perdew correlation (BP) with triple numerical set plus polarization functions (TNP) and homodesmotic reactions were employed to calculate cage strain energies, gaseous phase formation enthalpies of several silicon-based CL-20 derivatives. Comparative studies were carried out between silicon-based CL-20 nitro and difluoramine derivatives. The structural stability of these silicon-based CL-20 derivatives were evaluated in terms of NNO2 or NNF2 bond dissociation energies and Mulliken charges of NO2 or NF2 groups by means of density functional theory revised versions of the Perdew–Burke–Ernzerhof (RPBE) with TNP functions, and the exchange component of Perdew and Wangʹs 1991 functional (PW91) with TNP functions, two theoretical methods were chosen according to experimental data. The theoretical studies show that their performances are better than CL-20 in terms of detonation velocities, detonation pressures and explosion temperatures. Structural stability of these silicon-based CL-20 derivatives is higher than CL-20 according to NNO2 or NNF2 bond dissociation energies and cage strain energies. This work will lay some foundations for the future explorations of novel high-energy silicon-based compounds.