Density functional theory study of high‐pressure effect on crystalline 4,4′,6,6′‐tetra(azido)hydrazo‐1,3,5‐triazine

Abstract

Periodic density functional theory calculations are performed to study the hydrostatic compression effects on the structure, electronic, and thermodynamic properties of the energetic polyazide 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT) in the range of 0-100 GPa. At the ambient pressure, the local density approximation/Ceperley-Alder exchange-correlation potential parameterized by Perdew and Zunger relaxed crystal structure compares well with the experimental results. The predicted heat of sublimation is 38.68 kcal/mol, and the evaluated condensed phase of formation (414.04 kcal/mol) approximates to the experimental value. The detonation velocity and detonation pressure for the solid TAHT are calculated to be 7.44 km/s and 23.71 GPa, respectively. When the pressure is exerted less than 35 GPa, the crystal structure and geometric parameters change slightly. However, at 36 GPa, the molecular structure, band structure, and density of states change abnormally because of the azide-tetrazole transformation that has not been observed in gas phase or polar solvents. The azido group cyclizes to form a five-membered tetrazole ring that is coplanar with the riazine ring and contributes to a larger conjunction system. As the pressure augments further to 80 GPa, the hydrogen transfer is found and a new covalent bond H2-N9 is formed. In the studied pressure range, the band gap decreases generally except for some breaks due to the molecular transformation and drops to nearly zero at 100 GPa, which means the electronic character of the crystal changes toward a metallic system. An analysis of the electronic structure shows that an applied pressure increases the impact sensitivity of TAHT.

Multistep Thermolysis Mechanisms of Azido-s-triazine Derivatives and Kinetic Compensation Effects for the Rate-Limiting Processes

“…The electronic structures, detonation properties, and pyrolysis mechanism of TAHT and its hypothesized derivatives have been investigated using density functional theory (DFT, B3LYP) . It has been found that TAHT has better thermal stability than its analogue TAAT, which is in agreement with the experiments. − Further theoretical investigations have been carried out for both TAHT and TAAT in terms of their geometric and electronic parameters by considering the effect of the crystalline field. , TAHT has a theoretical heat of sublimation of 38.68 kcal mol –1 , while its detonation velocity and detonation pressure in the solid state are predicted to be 7.44 km s –1 and 23.71 GPa, respectively. An analysis of the electronic structure reveals that the impact sensitivity of TAHT and TAAT could be increased under pressure.…”

“…It has been found that TAHT has better thermal stability than its analogue TAAT, which is in agreement with the experiments [19][20][21] . Further theoretical investigations have been carried out for both TAHT and TAAT in terms of their geometric and electronic parameters by considering the effect of the crystalline field 22,23 . TAHT has theoretical heat of sublimation of 38.68 kcal mol -1 , while its detonation velocity and detonation pressure in solid state are predicted to be 7.44 km s -1 and 23.71 GPa,…”

Preparation, morphologies and thermal behavior of high nitrogen compound 2-amino-4,6-diazido-s-triazine and its derivatives

“…It has been found that TAHT has better thermal stability than its analogue TAAT, which is in agreement with the experimental results [26,27]. Further theoretical investigations have been carried out for both TAHT and TAAT in terms of their geometric and electronic parameters by considering the effect of the crystalline field [28,29]. Another compound which contains 4,6-diazido-1,3,5-triazineyl group is 4,6-diazido-N-(2,4,6-trinitrophenyl)-1,3,5-triazin-2-amine (TANDAzT).…”

Effects of Electronic Delocalization and Hydrostatic Compression on Structure and Properties of Cage Compound 4‐Trinitroethyl‐2,6,8,10,12‐pentanitrohexaazaisowurtzitane

“…In the past decades, our group has done lots of studies about high energetic materials on various properties . Among them, a nitro cage compound, namely 4‐trinitroethyl‐2, 6, 8, 10, 12‐pentanitrohexaazaisowurtzitane (TNE‐CL‐20) (in Figure ) prepared in recent years (in Figure ), was researched on its structural and energetic properties in gas phase .…”