Directional Interactions of α‐Particles with FOX‐7. A DFT Study

FOX‐7 is exposed to the effects of α‐particles from selected directions of approach. Various energies and properties of these composite FOX‐7 systems (FOX‐7+α‐particle) are obtained. The effect of α‐particles on FOX‐7 is drastic. The CC double bond turns into a single bond and one of the C NO₂ bonds highly elongates. The approach from the side of amino groups results more stable composite system compared to the approach from the side of nitro groups.     

DFT and MP2 Study of Intermolecular Interaction of 5‐Aminotetrazole and Hydrazine: Enthalpy of Formation of Hydrazinium 5‐Aminotetrazolate in the Gas Phase

The tautomerism of all possible forms of 5‐aminotetrazole ( AT1 – AT7 ) in the gas phase and continuum solvent was studied theoretically. The calculations were separately performed at the MP2 and CAM‐B3LYP levels of theory, using the 6‐311++G(d,p) basis set. It was found that 5‐aminotetrazole in the 2H form ( AT1) is the most stable isomer in both the gas phase and in solution. In addition, the aggregation of various isomers of 5‐aminotetrazole with hydrazine was investigated in the gas phase and in solution. Finally, the standard enthalpy of formations of the different structures of hydrazinium 5‐aminotetrazolate was determined in the gas phase. Using the calculated standard enthalpy of formation of different structures of hydrazinium 5‐aminotetrazolate in the gas phase and considering their Boltzmann population ratios, a single value has been reported for the standard enthalpy of formation of hydrazinium 5‐aminotetrazolate considering all of the tautomers. The calculated values are in excellent agreement with the experimentally reported heat of formation for the hydrazinium 5‐aminotetrazolate.     

Chromophores of neutral and dicationic thiophene-based oligomers – A study by first-principle methods

Time-dependent density functional theory (TD-DFT) and semiempirical methods (ZINDO-CIS, PPP-CIS) were applied to colored neutral and dicationic thiophene-based oligomers; in addition to the parent oligothiophenes and various ,′-end-capped derivatives, oligothiophenes with thiophene rings linked by methine, vinylene or phenylene groups were studied. Being π-chromophores, the compounds absorbed intensely in the Vis–NIR region; variation of the absorption energy with the reciprocal of the number of thiophene rings resulted in low band gap (as is known for low band gap polymers). Whilst the parent oligothiophenes displayed no singlet/singlet instability up to the octadecithiophene, the long chain oligomers were singlet/triple unstable. According to BS-UDFT calculations, biradical oligomers (two-plarons) were slightly favored over conventional dications (bipolarons). The color-determining electronic transitions of large size oligothiophenes calculated by open shell TD-DFT were little shifted in energy relative to those calculated using closed shell TD-DFT. The electronic structure of the oligomers is discussed in terms of bond length alternation and nucleus-independent chemical shifts.     

Struktur und spektrale Eigenschaften des Pentamethinmerocyanins 5‐(Dimethylamino)pentadienal in Lösung – Eine kombinierte DFT–SCI–SCRF–Studie

In order to estimate the solvent effect on molecular structure and on NMR and UV spectral data of 5‐(dimethylamino)penta‐2,4‐dien‐al(1) ( 1 , R = Me) the compound was calculated by first‐principles methods. Density functional theory was employed for structural optimization with solvent effects simulated by the recently refined COSMO continuum model. According to the calculations the molecular structure of 1 (R = Me) is noticeably affected by polar solvents resulting in a reduced bond length alternation. The relaxation of the molecular geometry in polar solvents is clearly reflected in the calculated ¹³C NMR chemical shifts calculated by GIAO‐DFT and in the absorption wave numbers of the intense lowest‐energy electronic transition calculated by SCI. Although the optimum geometry of the solute molecule in the solvents was calculated the magnitude of the solvatochromic shift is underestimated. The calculated solvatochromic effect in water is enhanced if the specific solvent‐solute interactions are considered by addition of one water molecule to 1 (R = Me) in the solvent cavity.     

Theoretical Studies on Molecular and Explosive Properties of 4,4′,5,5′‐Tetranitro‐2,2′‐bi‐1H‐imidazole (TNBI)

We performed theoretical studies to predict the molecular structure, molecular properties, and explosive performance of 4,4′,5,5′‐tetranitro‐2,2′‐bi‐1H‐imidazole (TNBI). High levels of ab initio and density functional theories were employed to predict the molecular structure of TNBI. Predicted TNBI structure was in good agreement with that observed by X‐ray crystallography. Heat of formation in the solid phase at 298 K was predicted to be 270.3 kJ/mol. Density of TNBI was predicted to be 1.919–1.956 g/cm³ depending upon the parameter sets of group additivity method. By using these values as input data, we estimated detonation velocity and C–J pressure to be 8.69–8.80 km/s and 34.5‐36.1 GPa, respectively. Impact sensitivity of TNBI was predicted to be 33 cm.     

A Computational Study of Density of Some High Energy Molecules

The detonation pressure depends quadratically on the loading density of the explosives. A precise estimate of the density is thus crucial to decide if a novel energetic material is worth pursuing. In this work we investigate theoretically the crystal densities of the energetic compounds RDX, TNT, NTO, DNAM, CL‐20, DADNE, and HMX. We calculate the crystal densities by using Materials Studio 7.0 Polymorph Predictor, employing force fields and exploring molecular packing arrangements with minima in total energy. Geometry optimized molecular structures computed by density functional theory (DFT) are used as input to the density predictions. In an additional DFT study we apply two functionals, B3LYP and M06 with the 6‐31G(d) and the 6‐31G(d,p) basis sets, and the program package GAUSSIAN09. In this part of the work crystal densities are calculated by using the molecular isosurface volume (defined by the volume within a surface with an electron density of 0.001 electrons per Bohr³) alone or combined with the variance of the electrostatic potential (ESP). The Polymorph Predictor seems to overestimate the densities, but the values are very dependent on the force field strength determined by charges assigned to atoms. In the GAUSSIAN09 DFT study the densities derived by using the M06 functional are in similar agreement with experimental data as what we experienced for the B3LYP results, although both functionals appear to give slightly lower densities than reported experimentally for the majority of the molecules. On average, the densities derived by the ESP method correlate equally well with measured values as the results obtained by the isosurface method.     

KDNP – A Lead Free Replacement for Lead Styphnate

Efforts directed towards creating new environmentally friendly replacements for existing primary explosives have resulted in development of potassium 5,7‐dinitro‐[2,1,3]‐benzoxadiazol‐4‐olate 3‐oxide (KDNP). The chemical and physical properties of this material have been investigated and it appears that KDNP is a suitable drop‐in replacement for lead styphnate in a variety of ordnance applications. KDNP is easily prepared, has excellent thermal stability and has safety and performance properties, which are equivalent to or exceed those for lead styphnate. KDNP has been qualified for military use per NAVSEAINST 8020.5C.     

Synthesis and Energetic Properties of Bis‐(Triaminoguanidinium) 3,3′‐Dinitro‐5,5′‐Azo‐1,2,4‐Triazolate (TAGDNAT): A New High‐Nitrogen Material

This paper describes the synthesis and characterization of bis‐(triaminoguanidinium)‐3,3′‐dinitro‐5,5′‐azo‐1,2,4‐triazolate (TAGDNAT), a novel high‐nitrogen molecule that derives its energy release from both a high heat of formation and intramolecular oxidation reactions. TAGDNAT shows promise as a propellant or explosive ingredient not only due to its high nitrogen content (66.35 wt.‐%) but also due to its high hydrogen content (4.34 wt.‐%). This new molecule has been characterized with respect to its morphology, sensitivity properties, explosive, and combustion performance. The heat of formation of TAGDNAT was also experimentally determined. The results of these studies show that TAGDNAT has one of the fastest low‐pressure burning rates (at 6.9 MPa) measured till date, 6.79 cm s⁻¹ at 6.9 MPa (39% faster than triaminoguanidinium azotetrazolate (TAGzT), a comparable high‐nitrogen/high‐hydrogen material). Furthermore, its pressure sensitivity is 0.507, a 33% reduction compared to TAGzT.     

Thermochemistry of biodiesel oxidation reactions: A DFT study

Density functional theory (DFT) quantum chemical calculations have been used to evaluate the gas phase electronic and thermochemical properties of fatty acid esters. The calculated low relative energies of the corresponding radicals can explain the large variety of oxidation products observed in experiments. The first oxidation reaction step was determined to be non-spontaneous for all fatty acid esters studied. Ethyl and methyl esters showed similar susceptibilities to oxidation in the gas phase. All subsequent reaction steps leading to the secondary products of oxidation were observed to be spontaneous. The thermochemical stability order of one double bond oxidation in the gas phase was determined to be linoleate < γ-linolenate < α-linolenate < oleate < ricinoleate. Therefore, biodiesel produced from castor oil could be used as an additive to biodiesel produced from other vegetable oil sources in order to improve the oxidation stability properties of the final fuel blend.     

Potential-induced lifting of the Au(1 0 0)-surface reconstruction studied with DFT

The potential-induced surface reconstruction of Au(1 0 0) was studied by a combination of density functional theory (DFT) and thermodynamic considerations. On the basis of realistic models for the reconstructed surface ((5 × 1) and (7 × 1) unitcells), in which a hexagonal overlayer was located above the bulk-truncated Au(1 0 0) surface, we found that applying an electric field causes a slight lifting of the overlayer, leading to a stronger surface buckling than without electric field. Using experimental cyclovoltammetry measurements we were able to relate the electric field applied in our calculations to the electrode potential. The resulting surface free energy curves showed a transition from the hexagonal-reconstructed surface phase to the non-reconstructed structure between +0.5 and +0.6 V (versus SCE-electrode) depending on the ion concentration in the electrolyte. Higher potentials values are required at lower electrolyte concentrations.     

Radical Scavenging Potential of the Phenothiazine Scaffold: A Computational Analysis

The reactivity of phenothiazine ( PS ), phenoselenazine ( PSE ), and phenotellurazine ( PTE ) with different reactive oxygen species (ROS) has been studied using density functional theory (DFT) in combination with the QM-ORSA (Quantum Mechanics-based Test for Overall Free Radical Scavenging Activity) protocol for an accurate kinetic rate calculation. Four radical scavenging mechanisms have been screened, namely hydrogen atom transfer (HAT), radical adduct formation (RAF), single electron transfer (SET), and the direct oxidation of the chalcogen atom. The chosen ROS are HO^., HOO^., and CH₃OO^.. PS , PSE , and PTE exhibit an excellent antioxidant activity in water regardless of the ROS due to their characteristic diffusion-controlled regime processes. For the HO^. radical, the primary active reaction mechanism is, for all antioxidants, RAF. But, for HOO^. and CH₃OO^., the dominant mechanism strongly depends on the antioxidant: HAT for PS and PSE , and SET for PTE . The scavenging efficiency decreases dramatically in lipid environment and remains only significant (via RAF) for the most reactive radical (HO^.). Therefore, PS , PSE , and PTE are excellent antioxidant molecules, especially in aqueous, physiological environments where they are active against a broad spectrum of harmful radicals. There is no advantage or significant difference in the scavenging efficiency when changing the chalcogen since the reactivity mainly derives from the amino hydrogen and the aromatic sites.     

Autoxidation of Methyl α-Eleostearate – Identification of the Low Molecular Weight Decomposition Products

Methyl α-eleostearate dissolved in pentane was stored at room temperature in the darkness. The low molecular weight products formed were compared with those resulting form reductive ozonolysis of methyl α-eleostearate. Pentanal, 2(E)-heptenal, 2(E),4(E)-nonadienal, methyl 9-oxononanoate, methyl 11-oxo-9(Z)-undecenoate and methyl 13-oxo-9(Z), 11(E)-tridecadienoate were formed in both processes. The storage experiment also yielded isomers of 2,4-nonadienal and methyl 13-oxo-9, 11-tridecadienoate, whose sterochemistry was not clarified.     

Decomposition and Ignition of the High‐Nitrogen Compound Triaminoguanidinium Azotetrazolate (TAGzT)

The high‐nitrogen compound triaminoguanidinium azotetrazolate (TAGzT) belongs to a class of C, H and N compounds that are free of both oxygen and metal, but retain energetic material properties as a result of their high heat of formation. Its decomposition thus lacks secondary oxidation reactions of carbon and hydrogen. The fact that TAGzT is over 80% nitrogen makes it potentially useful as a gas generant and energetic material with a low flame temperature to increase the impulse in gun or rocket propellants. The burning rate, laser ignition and flash pyrolysis (T‐jump/FTIR spectroscopy) characteristics were determined. It was found that TAGzT exhibits one of the fastest low‐pressure burning rates yet measured for an organic compound. Both the decomposition and ignition behavior of TAGzT are dominated by condensed phase reactions. T‐Jump/FTIR spectroscopy indicates that condensed phase reactions release about 65% of the energy, which helps to explain the high burning rate at low pressure.     

Understanding the Electronic Structure of Larger Azaacenes through DFT Calculations

Although azapentacenes have been widely demonstrated as promising candidates for n-type organic semiconductor devices, the exploration of larger azaacenes is still a challenge. In particular, theoretical studies on the electronic structures of larger azaacenes and the influence of N substitution on the ground states are still rare. Herein, we reported our investigation on the electronic ground-state characters of larger azaacenes through density functional theory (DFT) calculations. Our results indicated that larger azaacenes (fused aromatic rings larger than 6) would show open-shell singlet biradical characters and the introduction of more N atoms into the backbone of large acenes could favor their closed-shell ground states. Interestingly, azahexacenes with three or more N atoms (compounds N64–N68) and azaheptacenes (compound N74) with fourteen N atoms displayed closed-shell singlet ground states compared with the open-shell singlet diradical ground states for larger acenes. Our theoretical studies may guide the design and synthesis of larger azaacenes, which are the promising n-type organic semiconducting materials.     

A Proline-Based Neuraminidase Inhibitor: DFT Studies on the Zwitterion Conformation, Stability and Formation

The designs of potent neuraminidase (NA) inhibitors are an efficient way to deal with the recent “2009 H1N1” influenza epidemic. In this work, density functional calculations were employed to study the conformation, stability and formation of the zwitterions of 5-[(1R,2S)-1-(acetylamino)-2-methoxy-2-methylpentyl]-4-[(1Z)-1-propenyl]-(4S,5R)-d-proline (BL), a proline-based NA inhibitor. Compared to proline, the zwitterion stability of BL is enhanced by 1.76 kcal mol⁻¹ due to the introduction of functional groups. However, the zwitterion of BL will not represent a local minimum on the potential energy surface until the number of water molecules increases up to two (n = 2). With the addition of two and three water molecules, the energy differences between the zwitterions and corresponding canonical isomers were calculated at 3.13 and −1.54 kcal mol⁻¹, respectively. The zwitterions of BL are mainly stabilized by the H-bonds with the water molecules, especially in the case of three water molecules where the carboxyl-O atoms are largely coordination-saturated by three H-bonds of medium strengths, causing the zwitterion stability even superior to the canonical isomer. With the presence of two and three water molecules, the energy barriers for the conversion processes from the canonical isomers to the zwitterions are equal to 4.96 and 3.13 kcal mol⁻¹, respectively. It indicated that the zwitterion formation is facile to take place with addition of two molecules and further facilitated by more water molecules. Besides, the zwitterion formation of BL is finished in a single step, different from other NA inhibitors. Owing to the above advantages, BL is a good NA inhibitor candidate and more attention should be paid to explorations of BL-based drugs.     

A DFT Study on the Structures and Energies of Isomers of 4‐Amino‐1,3‐dinitro‐1,2,4‐triazol‐5‐one‐2‐oxide: New High Energy Density Compounds

Isomers of 4‐amino‐1,3‐dinitrotriazol‐5‐one‐2‐oxide (ADNTONO) are of interest in the contest of insensitive explosives and were found to have true local energy minima at the DFT‐B3LYP/aug‐cc‐pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazol‐5‐one N‐oxides were obtained in their ground state. Kamlet‐Jacob equations were used to evaluate the performance properties. The detonation properties of ADNTONO (D=10.15 to 10.46 km s⁻¹, P=50.86 to 54.25 GPa) are higher compared with those of 1,1‐diamino‐2,2‐dinitroethylene (D=8.87 km s⁻¹, P=32.75 GPa), 5‐nitro‐1,2,4‐triazol‐3‐one (D=8.56 km s⁻¹, P=31.12 GPa), 1,2,4,5‐tetrazine‐3,6‐diamine‐1,4‐dioxide (D=8.78 km s⁻¹, P=31.0 GPa), 1‐amino‐3,4,5‐trinitropyrazole (D=9.31 km s⁻¹, P=40.13 GPa), 4,4′‐dinitro‐3,3′‐bifurazan (D=8.80 km s⁻¹, P=35.60 GPa) and 3,4‐bis(3‐nitrofurazan‐4‐yl)furoxan (D=9.25 km s⁻¹, P=39.54 GPa). The  NH₂ group(s) appears to be particularly promising area for investigation since it may lead to two desirable consequences of higher stability (insensitivity), higher density, and thus detonation velocity and pressure.     

Theoretical studies of pentene cracking on zeolites: C–C β-scission processes

The C–C bond-breaking step of pentene adsorbed on a model zeolite cluster is examined using ab initio and density functional theory (DFT/B3LYP) electronic structure techniques as an example of the β-scission process that arises in cracking of alkanes and alkenes. After pentene has been protonated by the acid site, the reactant for the cracking process corresponds to a pentyl cation covalently bound to the oxygen of the zeolite, ZO⁻–C₅H⁺₁₁. The product of the C–C bond-breaking process is propene plus an ethyl cation bound to a neighboring oxygen. The energy of the transition state relative from B3LYP calculations is 60 kcal/mol relative to the pentyl cationic reactant. For the case of the branched olefin methyl pentene, the transition state energy is slightly lower (55 kcal/mol), but the overall reaction energy is essentially the same as for pentene. The results are compared to the case of the gas phase pentyl carbenium ion.     

以非离子表面活性剂为高效催化剂的TEX合成工艺研究

以甲酰胺和质量分数40%的乙二醛为原料,经缩合反应得到1,4-二(甲酰基)-2,3,5,6-四羟基哌嗪(DFTHP),然后在硝硫混酸作用下,合成了4,10-二硝基-2,6,8,12-四氧杂-4,10-二氮杂四环[5.5.0.05,9.03,11]十二烷(TEX),并用FTIR光谱、核磁共振对其结构进行表征。研究了硝硫混酸体积比、硝化反应温度、非离子型表面活性剂种类及用量对TEX收率和纯度的影响。得到最优合成条件为:发烟硝酸与浓硫酸的体积比为4∶3、加样温度45℃、硝化温度55℃、以聚乙二醇400(PEG400)为反应催化剂,且PEG400与DFTHP的质量比为0.15∶1.00,此时TEX收率为59.8%,纯度为99.2%。     

A theoretical investigation on the properties of the new poly(N‐vinylcarbazole)‐3‐methylthiophene (PVK‐3MeT) synthesized graft copolymer

In this article, we present quantum chemical calculations, based on density functional theory (DFT), performed to investigate the geometries and the opto‐electronic properties of a new synthesized graft copolymer based on poly(N‐vinylcarbazole) (PVK) and poly(3‐methylthiophene) (PMeT) named PVK‐3MeT. First, we have theoretically computed and compared the structural, optical, and vibrational parameters of both neutral and doped states. In addition, the excited state was theoretically obtained by the ab initio RCIS/STO‐3G method. To assign the absorption and emission peaks observed experimentally, we computed the energies of the lowest singlet excited state with the time‐dependent density functional theory (TD‐DFT) method. Electronic parameters such as the HOMO‐LUMO band gap, the ionization potential (IP), and electron affinity (EA) are extracted. Calculations show that the PVK‐3MeT copolymer is nonplanar in its ground neutral state. Meanwhile, upon doping or photoexcitation, an enhancement of the planarity is observed, resulting on a decrease of the inter‐ring torsion angle between 3‐methylthiophene units. Such modifications in the geometric parameters induce a dramatic change on the HOMO and LUMO orbitals in the doped or excited states. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A DSC Analysis of Inverse Salt‐pair Explosive Composition

Alkali nitrates are used as an ingredient in low explosive compositions and pyrotechnics. It has been suggested that alkali nitrates can form inverse salt‐pair explosives with the addition of ammonium chloride. Therefore, the thermal behavior of low explosive compositions containing potassium nitrate mixed with ammonium chloride has been studied using Differential Scanning Calorimetry (DSC). Results provide information about the ion exchange reaction between these two chemical substances and the temperature region at which the formation of a cloud of salt particles of potassium chloride takes place. Furthermore, the addition of ammonium chloride quenches the flame of deflagrating compositions and causes the mixture to undergo explosive decomposition at relatively low temperatures.