Theoretical Studies on the Structure and Detonation Properties of a Furazan-based Energetic Macrocycle Compound

Based on the full optimized molecular geometric structure at 6-311++G** level,the density(ρ),detonation velocity(D),and detonation pressure(P) for a new furazan-based energetic macrocycle compound,hexakis[1,2,5]oxadi-azole[3,4-c:3',4'-e;3',4'-g:3'',4''-k:3',4'-m:3'',4''-o][1,2,9,10]-tetraazacyclohexadecine,were investigated to verify its capacity as high energy density material(HEDM). The infrared spectrum was also predicted. The heat of formation(HOF) was calculated using designed isodesmic reaction. The calculation on the bond dissociation energies(BDEs) was done and the pyrolysis mechanism of the compound was studied. The result shows that the N_3–O_1 bond in the ring may be the weakest one and the ring cleavage is possible to happen in thermal decomposition. The condensed phase HOF and the crystal density were also calculated for the title compound. The detonation data show that it can be considered as a potential HEDM. These results would provide basic information for the molecular design of novel high energy materials.     

Theoretical Investigations on the Structure,Density, Thermodynamic and Performance Properties of Bis（2,2-dinitropropyl） formal

Density functional method was used to investigate the IR spectrum,heat of formation and thermal stability of a new energetic material bis(2,2-dinitropropyl) formal(BDNPF).The detonation velocity and pressure were evaluated by using the Kamlet-Jacobs equations based on the theoretical density and heat of formation.The bond dissociation energies for the weakest bonds were analyzed to investigate the thermal stability of the title compound.The results show that the C(1)-N(1) bond is predicted to be the trigger bond during pyrolysis.The crystal structure obtained by molecular mechanics belongs to the P21 space group,with the lattice parameters to be Z = 2,a = 11.5254,b = 6.2168,c = 9.5000  and ρ= 1.66 g/cm3.     

Theoretical Study on the Nitrogen-rich Derivatives Based on 1,2,4-Triazole and 1,2,3-Triazole Rings: an Extended Family of Power Performance Energetic Materials

The geometric and electronic structures of the derivatives of 4-nitro-5-(5-nitroimino-1,2,4-triazol-3-yl)-2H-1,2,3-triazolate (named A～J) are explored employing density functional theory (DFT) calculations at the B3LYP/6-311G**level of theory.Based on the optimized molecular structures,the heats of formation (HOF) are obtained,and the electronic properties,density and molecular sensitivity by characteristic heights (H_(50)) are discussed.Besides,the detonation performances (detonation velocity,detonation pressure) are estimated via Kamlet-Jacobs (K-J) formula.Compounds B (H_(50)=29.4 cm,ρ=1.91 g/cm~3,Q=1563.04 cal/g,P=36.05 GPa,D=8.95 km/s) and H (H_(50)=31.9 cm,ρ=1.80 g/cm~3,Q=1610.09 cal/g,P=37.31 GPa,D=9.12 km/s) have positive HOFs and remarkable insensitivity and good detonation performance,strongly suggesting them as the acceptable new-type explosive.The initiating power surpasses conventional primary explosives,such as HMX.The outstanding detonation power of compounds B and H contributes to its future prospects as a promising green primary explosive.     

Theoretical Exploration on Structural Stabilities and Detonation Properties of Nitrimino Substituted Derivatives of Cyclopropane

The packed density, detonation velocities, and detonation pressures of a series of cyclopropane derivatives were investigated to look for high energy density compounds. For exploring the possibility of synthesis, the bond order, heats of formation(HOF), bond dissociation energy(BDE), and characteristic height were calculated. Based on our results, A_3 has the best detonation characters. Both A_1 and A_2 showed comparative detonation parameters and compact sensitivity with RDX, and could be regarded as the candidates of high energy density molecules.Both the heats of formation and explosive heats rose with the increase of nitrimino groups and the strain energy of three-membered ring. For A_1 compound, pyrolysis mechanism might be a mix one(breakages of C–C and N–NO_2 bonds). However, for A_2 and A_3 compounds, the N–NO_2 is the trigger bond in explosive reactions. Our results may provide the basic information for further study of this kind of compounds.     

An ab initio Study on the Structural and Bonding Properties of Li_2Si_3O_7

A theoretical study on the structural and electronic properties of Li2Si3O7 is performed by using density functional theory(DFT) method.The molecular structure of the crystal and two kinds of [SiO4]-tetrahedra with different number of non-bridging oxygen(Qn) are analyzed.The structure of crystal Li2Si3O7 can be considered as a framework of corner-sharing tetrahedra.From the band structure(BS),total density of state(TDOS) and projected density of state(PDOS) of the crystal,the structures of Q3,Q4,and LiO4 tetrahedra as well as their bonding characters are presented.For lithium trisilicate,we find the bond cation-NBO(nonbridging oxygen and oxygen atoms bonding to one silicon atom only) is stronger than the bond cation-BO(bridging oxygen and oxygen atoms bonding to two silicon atoms).By analyzing the ionicity of two different types of bonds of silicon-oxygen according to the Mulliken population analysis,we also find that the Si-NBO bonds have higher ionicity than Si-BO for crystalline lithium trisilicate,which agrees with other lithium silicates.     

Theoretical Exploration about the Detonation Performance and Thermal Stability of the Nitro-substituted Derivatives of Guanine

The nitro-substituted derivatives of guanine are designed and calculated to explore novel high energy density materials. To explore the thermal stability of title molecules, the heat of formation(HOF), bond dissociation energy(BDE), and bond order of the trigger bond are calculated. To predict the possibility used as high energy density compounds, the detonation pressure(P), detonation velocity(D), explosive heat(Q), and crystal density(ρ) are calculated by using the classical Kamlet-Jacobs(K-J) equation. Based on our calculations, E(D = 8.93 km/s, P = 37.21 GPa) is confirmed as the potential high energy density compound.     

Kinetic Study on the Exothermic First-stage Decomposition Reaction of 2,4,8,10-Tetranitro-2,4,8,10-tetraaza- spiro[5,5]undecane-3,9-dione

Introduction 2,4,8,10-Tetranitro-2,4,8,10-tetraazaspiro[5,5]udecane- 3,9-dione is a typical cyclourea nitramine (Figure 1). Its crystal density is 1.91 gcm-3. The detonation velocity according to =1.90 gcm-3 is about 8670 ms-1. Its sensitivity to impact is better than that of cyclotrimethy- lenetrinitramine. So it is the potential high explosive. Its preparation,1-3 properties,1-3 hydrolytic behavior4 and electronic structure3 have been reported. In the present work, we report its kinetic pa…     

Kinetics and Mechanism of Exothermic First-stage Decomposition Reaction for 2,6-Dinitro-4,8-bis（2,2,2-trinitroethyl）-2,4,6,8-tetraazabicyclo[3.3. 1]nonane-3,7-dionel

2,6-Dinitro-4,8-bis(2,2,2-trinitroethyl)-2,4,6,8-tetraazabicyclo[-3. 3.1]nonane-3, 7-dionel is a typical cyclourea nitramine. Its crystal density is 1.94g/cm^3. The detonation velocity corresponding to ρ=1.920g/cm^3 is about 8957 m/s. It has the potential application as high explosive due to the above-mentioned high performance. Its prepara-tion, properties and hydrolytic behavior have     

Addition Reactivity of C_（36） Cage Controlled by the Curvature and the Electronic Factors：A DFT Study

The molecular geometries and electronic structures of the fullerene derivatives C36(OH)n(n = 1～2) have been investigated on the basis of density functional theory calculation at the B3LYP/6-31++G* level.The geometry optimization results indicate that the location of C2 atom is the most active site in the three potential adding patterns,and the C1 or C2 site has a larger binding energy than C3 for the addition reactions of C36(D6h) cage and OH radicals resulting from the larger curvature.The electronic structure calculation results disclose that the C2 site has larger electronic population in HOMO and larger spin density,and the addition reaction on the C2 site need overcome a lesser energy gap than that on the C1 or C3 site.Thus,the addition is controlled jointly by the curvature and the electronic factors.Besides,when two hydroxyls are added to the C36 surface,the C2 sites are also the most active locations.The most stable addition adduct of C36(OH)2 is the isomer which holds Ci symmetry,and the spin multiplicity seriously affects the stabilities of the adducts.     

Thermochemical Properties and Non-isothermal Decomposition Reaction Kinetics of N-Guanylurea Dinitramide （GUDN）

Introduction N-Guanylurea dinitramide (GUDN) is a new ener-getic oxidizer with higher energy and lower sensitivity. Its crystal density is 1.755 g·cm-3. The detonation velocity is about 8210 m·s-1. Its specific impulse and pressure exponent are 213.1 s and 0.73, respectively. It has the potential for possible use as an energy ingredient of propellants and explosives from the point of view of the above-mentioned high performance. Its preparation,1 properties2 and hygroscopocity2 have been …     

Effect of charged and excited states on the decomposition of 1,1-diamino-2,2-dinitroethylene molecules

The authors have calculated the electronic structure of individual 1,1-diamino-2,2-dinitroethylene molecules (FOX-7) in the gas phase by means of density functional theory with the hybrid B3LYP functional and 6-31+G(d,p) basis set and considered their dissociation pathways. Positively and negatively charged states as well as the lowest excited states of the molecule were simulated. They found that charging and excitation can not only reduce the activation barriers for decomposition reactions but also change the dominating chemistry from endo- to exothermic type. In particular, they found that there are two competing primary initiation mechanisms of FOX-7 decomposition: C-NO2 bond fission and C-NO2 to CONO isomerization. Electronic excitation or charging of FOX-7 disfavors CONO formation and, thus, terminates this channel of decomposition. However, if CONO is formed from the neutral FOX-7 molecule, charge trapping and/or excitation results in spontaneous splitting of an NO group accompanied by the energy release. Intramolecular hydrogen transfer is found to be a rare event in FOX-7 unless free electrons are available in the vicinity of the molecule, in which case HONO formation is a feasible exothermic reaction with a relatively low energy barrier. The effect of charged and excited states on other possible reactions is also studied. Implications of the obtained results to FOX-7 decomposition in condensed state are discussed.     

Critical detonation diameters of highly dispersed energetic substances

The relationship between the critical detonation diameters of energetic substances and their specific surface area was revealed from the results of studying the detonation ability of a series of energetic substances [pentaerythritol tetranitrate (TEN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), 2,4,6-trinitrophenylmethylnitramine (tetryl), benzotrifuroxan (BTF), hexanitrohexaazaisowurtzitane (CL-20), dinitrodifurazanylfuroxan (DNTF), dinitrodifurazanylfurazan (NTF), 1,1-diamino-2,2-dinitroethene (FOX-7)]. A mathematical expression for this relationship was suggested. The critical detonation diameters of highly dispersed (micrometer particles) energetic substances were determined by experiments and calculations. These diameters are in the range 0.06–0.8 mm, which makes these substances suitable for use in aerospace engineering, priming systems, detonation manifolds, and explosion logic devices.     

1,1-二氨基-2,2-二硝基乙烯的合成与性能研究

以2-甲基嘧啶-4,6-二酮为原料, 通过硝化和水解过程合成出FOX-7 (1,1-二氨基-2,2-二硝基乙烯), 经IR, MS, NMR和元素分析鉴定了其结构, 并对影响得率的主要因素进行了简要分析. 重结晶提纯后培养合成产物的单晶, 用四圆衍射仪对其进行了结构解析, 得到了合成产物的晶体学数据. 测试了FOX-7的电火花感度和落锤感度, 并同RDX (1,3,5-三硝基-1,3,5-三氮杂环己烷)、HMX(环四甲撑四硝胺)以及TATB(三氨基三硝基苯)进行了对比, 结果表明FOX-7的感度要低于RDX, 但较TATB差. 同时对原始样品和重结晶FOX-7的外观形貌和热性质进行了测试, 并对变化情况进行了说明, 发现FOX-7的外观形貌和热性质可以进一步改善和优化.     

DFT studies on 7-nitrotetrazolo [1,5]furazano[4,5-b]pyridine 1-oxide: crystal structure,detonation properties,sensitivity and effect of hydrostatic compression

A new high energy density compound 7-nitrotetrazolo[1,5]furazano[4,5-b]pyridine 1-oxide (NFP) was studied. The molecular geometrical and electronic properties, heat of formation and detonation properties were predicted. Two crystal polymorphs of NFP were also predicted and compared well with experimental results. According to the constitution of the frontier energy bands, the tetrazol ring of NFP may be the active position of thermolysis. The calculated band gaps indicate the sensitivity of α-NFP is slightly lower than that of β-NFP. The effects of hydrostatic compression on the more stable form α-NFP were investigated in the pressure range of 0–100 GPa. α-NFP has an anisotropic compressibility. The band gap reduction is more pronounced in the low-pressure region than in the high-pressure region and the gap drops to nearly zero at 15 GPa, which means that the crystal changes its electronic character toward a metallic system. The analysis of density of states indicates that the electronic nonlocality increases under the influence of pressure.     

N-脒基脲二硝酰胺盐晶体形貌的分子动力学研究

采用分子动力学方法,在正侧(NVT)系综下研究了N-脒基脲二硝酰胺盐(FOX-12)在溶剂中的晶体形貌.通过构建溶剂分子层-晶面的界面吸附模型模拟其动力学平衡构型,计算溶剂与晶体表面间的结合能,进而对真空附着能进行修正并获得溶剂条件下的晶貌.使用自然冷却法在水和水/甲醇中培养FOX-12晶体并利用扫描电子显微镜进行了表征.结果表明,在真空条件下决定FOX-12晶貌的6个重要晶面为(110),(200),(201),(011),(002)和(111);FOX-12在水溶液条件下的主要晶面为(110)和(011),在水/甲醇溶液条件下的主要晶面为(200)和(011),预测的晶体形貌与实验结果相吻合.对水分子和FOX-12的(110)面间的径向分布函数进行了计算,分析了水分子和晶面间的分子间作用力.     

K(FOX-7)·H_2O的合成、晶体结构和热行为

利用1,1-二氨基-2,2-二硝基乙烯(FOX-7)和KOH在甲醇水体系中合成了一种新型有机钾盐,并培养出K(FOX-7)·H2O单晶.该晶体属三斜晶系,P1空间群,晶胞参数:a=0.7493(2)nm,b=0.9767(3)nm,c=2.0035(5)nm,α=90.017(4)°,β=97.129(4)°,γ=90.019(4)°,V=1.4548(7)nm3,Dc=1.865g/cm3,μ=0.724mm-1,F(000)=832,Z=8,R1=0.0523,wR2=0.1082.K(FOX-7)·H2O的热分解行为可分为一个脱水和两个放热分解过程,且第一放热分解反应的表观活化能和指前因子分别为135.9kJ/mol和1012.17s-1.热爆炸的临界温度为212.02℃.同时,利用微量热法测定了K(FOX-7)·H2O的比热容,298.15K时的摩尔热容为210.88J·mol-1·K-1.用测得的比热容方程计算了298.15K为基础的FOX-7的热力学函数,并得到了绝热至爆时间为15.7～16.8s之间的某一值.     

Coupling effects of high temperature and pressure on the decomposition mechanisms of 1,1-diamino-2,2-dinitroehethe crystal: Ab initio molecular dynamics simulations

Recently, Dreger et al. experimentally investigated the phase diagram and decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7) single crystal compressed hydrostatically up to 10 GPa and heated over a range of 293–750 K (J. Phys. Chem. C 2016 , 120, 11092–11098). As a continuation, we performed ab initio molecular dynamic simulations to study the initiation mechanisms and subsequent decomposition of FOX-7 at a temperature of 504 K (initial decomposition temperature) coupled with a pressure of 1–5 GPa, 604 K at 5GPa, and 704 K at 5 GPa. However, our two compressing ways are different: the former is static hydrostatical compression, while our way is dynamic compression. Our results indicate that the initial decomposition mechanism was dependent on the temperature but independent of the pressure. The initial decomposition step is the bimolecular intermolecular hydrogen transfer. The subsequent decomposition of FOX-7 is sensitive to both the temperature and pressure. At 504 K, the decomposition of FOX-7 was accelerated from 1 to 2 GPa and from 3 to 5 GPa but decelerated from 2 to 3 GPa. The temperature exhibits a positive effect on the decomposition. Overall, the temperature and pressure have great cooperative effects on the decomposition of FOX-7. Our study may provide new insight into understanding the initial mechanisms and decomposition reactions of energetic materials at relatively low temperatures coupled with different pressures in atomic detail.     

Computational studies on the crystal structure, thermodynamic properties, detonation performance, and pyrolysis mechanism of 2,4,6,8-tetranitro-1,3,5,7-tetraazacubane as a novel high energy density material

Studies have suggested that octanitrocubane (ONC) is one of the most powerful non-nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro-1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm(3), and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P2(1)2(1)2(1), and the corresponding cell parameters are Z = 4, a = 8.87 ?, b = 8.87 ?, and c = 11.47 ?. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM.