Bond Dissociation Energies of Energetic Compounds: A Comparison of Theoretical Methods.

摘要

Due to their computational efficiency, density functional methods utilizing semiempirical hybrid functionals such as B3LYP are commonly used in calculating the molecular potential energy surfaces of a wide variety of molecules. In particular, potential energy surfaces of several energetic compounds such as hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX), 1,3,3- trinitroazetidine (TNAZ), 5-nitro-2,4-dihydro- 3H-1,2,4-triazolone (NTO), and 1, 1-diamino-2,2-dinitroethylene recently have been computed using density functional methods (B3LYP). These potential energy surfaces are used, for example, to predict the decomposition mechanisms and for constructing force fields for modeling and simulation of solid state phase transitions. The accuracy of B3LYP relative energies and structures is generally observed to be comparable to that obtained using second order perturbation theory methods. However, an unresolved issue is the reliability of density functional based methods in cases where a significant degree of multiconfigurational character may be present in the compounds of interest, such as in the energetic molecules listed above. The present study is a systematic comparison of several electronic structure methods in the prediction of bond dissociation energies of energetic molecules. In particular, the C-NO2 and C-NH2 bond dissociation energies of 1,1- diamino-2,2-dinitroethylene and its prototypes are used as a testbed for comparison of B3LYP with single configuration self-consistent field (SCF), second order perturbation theory (MP2), and coupled-cluster (CCSD(T)) calculations as well as multiconfigurational SCF (MCSCF) and quasi-dependent perturbation theory (MCQDPT) methods.