Density functional theory (DFT) periodic calculations were performed to study the geometrical and electronic structures of energetic compound dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) under the pressure ranging from 0 to 400 GPa. The optimized crystal structure by the local density approximation (LDA) with CA-PZ functional matches well with the experimental values under the ambient pressure. When the structural transformations occur under the pressure of 126, 288, and 334 GPa, with the pressure increasing, the lattice constants, unit cell volume, total energy, interatomic distances, bond angles, atomic charges, and bond populations of TKX-50 change gradually. First of all, TKX-50 is rearranged in the crystal and the improvement of the molecular planarity occurs. Next, structural transformation appears with the distortion of the tetrazole rings. Finally, the rotation of molecular conformation occurs. The results of the band gap and density of states show that TKX-50 crystal, with the increase of pressure, undergoes an electronic transition from the semiconductor to the metallic system. These results provide basic information for the high pressure behavior of crystalline TKX-50.

Teoria do funcional da densidade (DFT) foi empregada no estudo de poli-nitroimidazopiridinas em nível B3LYP/6-31+G(d). A velocidade (D) e a pressão de detonação (P) foram avaliadas utilizando as equações Kamlet-Jacobs (K-J) baseadas na densidade molecular teórica (r) e calor de formação (HOF). A estabilidade térmica dos compostos foi investigada através dos cálculos das energias de dissociação das ligações (BDE) em nível B3LYP/6-31+G(d) irrestrito. Alguns compostos apresentam altas densidades (ca. 1,95 g cm-3) e bons desempenhos. Os resultados das simulações revelam que duas das moléculas atuam similarmente ao 1,3,5,7-tetranitro-1,3,5,7-tetrazocano (HMX), e outras duas moléculas podem ser potenciais candidatas a compostos de alta densidade de energia (HEDCs). Estes resultados fornecem informações básicas para o planejamento molecular de novos compostos de alta densidade energética.

Density functional theory (DFT) was employed to study polynitroimidazopyridines at the B3LYP/6-31+G(d) level. Detonation velocity (D) and detonation pressure (P) were evaluated using Kamlet-Jacobs (K-J) equations based on the theoretical molecular density (r) and heat of formation (HOF). Thermal stability of the title compounds was investigated by calculating the bond dissociation energies (BDE) at the unrestricted B3LYP/6-31+G(d) level. Some compounds have high densities (ca. 1.95 g cm-3) and good performance. Simulation results reveal that two molecules perform similarly to 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), and other two molecules may be potential candidates of high energy density compounds (HEDCs). These results provide basic information for molecular design of novel high energetic density compounds.

The B3LYP/6-31G (d) density functional theory (DFT) method was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. Heat of formation (HOF) and calculated density were estimated to evaluate detonation properties using Kamlet-Jacobs equations. Thermal stability of 3,6,7,8-tetranitro-3,6,7,8-tetraaza-tricyclo [3.1.1.1(2,4)]octane (TTTO) was investigated by calculating bond dissociation energy (BDE) at the unrestricted B3LYP/6-31G(d) level. Results showed the N-NO2 bond is a trigger bond during the thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to P2(1)/C space group, with cell parameters a = 8.239 Å, b = 8.079 Å, c = 16.860 Å, Z = 4 and r = 1.922 g cm-3. Both detonation velocity of 9.79 km s-1 and detonation pressure of 44.22 GPa performed similarly to CL-20. According to the quantitative standards of energetics and stability, TTTO essentially satisfies this requirement as a high energy density compound (HEDC).