Computer simulations and analysis of structural and energetic features of crystalline cage energetic compound: 2, 4, 6, 8, 12-pentanitro-10-(3, 5, 6-trinitro (2-pyridyl))-2, 4, 6, 8, 12-hexaazatetracyclo [5.5.0.03,11 .05,9 ]dodecane

Abstract

First principles molecular orbital and plane-wave ab initio calculations have been used to investigate the structural and energetic properties of a new cage compound 2, 4, 6, 8, 12-pentanitro-10-(3, 5, 6-trinitro (2-pyridyl))-2, 4, 6, 8, 12-hexaazatetracyclo [5.5.0.03,11.05,9]dodecane (PNTNPHATCD) in both the gas and solid phases. The molecular orbital calculations using the density functional theory methods at the B3LYP/6-31G(d,p) level indicate that both the heat of formation and strain energy of PNTNPHATCD are larger than those of 2, 4, 6, 8, 10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazatetracyclo [5.5.0.0.0] dodecane (CL-20). The infrared spectra and the thermodynamic property in gas phase were predicted and discussed. The calculated detonation characteristics of PNTNPHATCD estimated using the Kamlet–Jacobs equation equally matched with those of CL-20. Bond-breaking results on the basis of natural bond orbital analysis imply that C–C bond in cage skeleton, C–N bond in pyridine, and N–NO2 bond in the side chain of cage may be the trigger bonds in the pyrolysis. The structural properties of PNTNPHATCD crystal have been studied by a plane-wave density functional theory method in the framework of the generalized gradient approximation. The crystal packing predicted using the Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force fields belongs to the Pbca space group, with the lattice parameters a = 20.87 A, b = 24.95 A, c = 7.48 A, and Z = 8, respectively. The results of the band gap and density of state suggest that the N–NO2 bond in PNTNPHATCD may be the initial breaking bond in the pyrolysis step. As the temperature increases, the heat capacity, enthalpy, and entropy of PNTNPHATCD crystal all increase, whereas the free energy decreases. Considering that the cage compound has the better detonation performances and stability, it may be a superior high energy density compound. Copyright © 2015 John Wiley & Sons, Ltd.