Theoretical evaluation of sensitivity and thermal stability for high explosives based on quantum chemistry methods: A brief review

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc.     

Influence of backbone conformations of human carbonic anhydrase II on carbon dioxide hydration: hydration pathways and binding of bicarbonate

In this study, the hydration of carbon dioxide and the formation of bicarbonate in human carbonic anhydrase II have been examined. From semiempirical QM/MM molecular dynamics studies, dominant conformations of the protein backbone, possibly contributing to the catalytic activity, have been isolated and further examined by means of density functional QM/MM methods. In agreement with experimental observations, a binding site for cyanate, which acts as an inhibitor, has been located, whereas for carbon dioxide, depending on the conformation of the protein environment, either a different binding site or no binding site has been found. In the latter case, carbon dioxide diffuses barrierless to the zinc-bound oxygen, and then a weakly bound bicarbonate complex is formed. The formed complex is characterized by a long C-O bond to the zinc-bound hydroxide. The nature of the calculated stationary points was verified by determination of vibrational frequencies. Finally, the dissociation of the formed bicarbonate from zinc has been considered. Therefore, a water molecule was included in the QM zone of the QM/MM hybrid potential, and minimization yielded a pentacoordinated intermediate. From a potential energy scan, an activation energy of 6.2 kcal/mol for dissociation of bicarbonate from Zn has been found.     

Recent applications of the ring-oven technique : A brief review

The ring-oven technique is a special type of spot analysis. In this review, papers published since 1976 are discussed. The aspects dealt with include developments in the technique and its use, the identification and determination of inorganic ions, organic substances, enzymatic analysis, applications to air and water samples, and combinations with other techniques.     

Extraction of nanofibers from polymer blends: A brief review

This review is about the naturally formed and intentionally produced nanofibrils or nanofibers (NFs) that have been extracted and utilized or expected to be used for special applications. The diameter of NFs ranges between a few to a few hundred nanometers. Methods to arrange synthetic NFs assembly in yarns or pads forms have been examined. High throughput productions, versatility of various thermoplastics, and less environmental pollution are the advantages of the methods of extraction, which seems to make it as an economical process. It can also be used for the polymers that are difficult to be converted to NFs by electrospinning. The process is challenging and scientifically fascinating to attract the investigators. There are many more polymers to be considered, and there are many more envisioned applications that have to be practiced in the future. A theoretical base is needed for the evaluation of the effects of polymer flow parameters on the extracted NFs properties.     

Proton shuttle efficiency of bicarbonate: A theoretical study on tautomerization and CO2 hydration

The efficiency of bicarbonate molecule (HCO₃⁻) as a proton shuttle in the tautomerization and (non)enzymatic CO₂ hydration reactions has been investigated with the aid of computational chemistry methods (DFT and ab initio). The results revealed that bicarbonate can decrease the barrier height of tautomerization (keto-enol, azo-hydrazo and imine-amine) more than 70%. This value is around 45% for water molecules. Also, HCO₃⁻ can catalyze the CO₂ hydration both inside (enzymatic) and outside (nonenzymatic) the active site of human carbonic anhydrases II (HCA II). In the absence of enzyme, bicarbonate molecule can lower the CO₂ hydration from ∼50 kcal mol⁻¹ in the gas phase to ∼14 kcal mol⁻¹ in the aqueous media. This reaction maintains its barrier (∼15 kcal mol⁻¹) for bicarbonate-Zn complex in the active site of enzyme; it has been observed that amino acid residues, mainly Thr199 and Glu106, are actively involved in the proton transfer network and facilitate CO₂ hydration ability of bicarbonate.     

Discotic liquid crystals. A brief review

Progress in the field of discotic liquid crystals is summarized, with emphasis on experimental results rather than theoretical developments. Examples are given of discotic mesogens (including metallo-mesogens) and discotic polymers, and the structures of the mesophases identified to date are described.     

A study of methanetetraol dehydration to carbonic acid

Two alternative dehydration reactions C(OH)₄ → (HO)₂CO + H₂O and C(OH)₄ + H₂O → (HO)₂CO + 2H₂O are studied by ab initio Becke3LYP/6–311 + G^** and MP2/6–31G^** methods. Calculated energy and geometry characteristics of intermediates and transition states predict a catalytic effect of one water molecule and the exothermism of the transformations. Relevant HF/6–311 + G^**, HF/6–31G^**, HF/6–31G, and HF/3–21G calculations were performed for comparison. © 1997 John Wiley & Sons, Inc.     

A brief review of the computational modeling of CO2 electroreduction on Cu electrodes

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铁钴三核原子簇氢化物HFe2Co(CO)9PR和HFe2Co(CO)9Se的合成

在THF 中反应, 合成了以有机膦作μ3-配位体的新型铁钴三核原子簇羰基氢化物HFe2Co(CO)9PR.又用高压法合成FeCo2(CO)2Se, 它与Na2[Fe(CO)4] 在THE 中反应, 得到另一个以硒作μ3-配位体的新型铁钴三核原子簇羰基氢化物式电离成-价阴离子, 再与反应生成     

Theoretical study on reaction mechanism of sulfuric acid and ammonia and hydration of (NH4)2SO4

In order to understand the mechanism of nucleation of (NH₄)₂SO₄ aerosol, the reaction between sulfuric acid and ammonia in the absence of water molecule is performed at M06/6-311++G(d,p) level. The results show that the (NH₄)₂SO₄ and NH₄HSO₄ units may exist instantaneously in gas phase without water molecule, which is a theoretical prediction that needs detection by further experiment. To further study the growth of the primary nuclei, the geometries, energies, and harmonic frequencies of (NH₄)₂SO₄ · (H₂O) _n (n = 0–9) are calculated both at M06/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The tendency of the theoretical vibration frequencies is in accordance with the experimental results. The influence of the water molecule on the properties of (NH₄)₂SO₄ is also analyzed. Our results indicate that M06 is more accurate than B3LYP for this kind of system. Moreover, the first principle molecular dynamics method is used to simulate the structural transformation for two representative isomers whose energies are close, to understand the relationship between solvent-shared ion pairs and contact ion pairs.     

A theoretical study of co insertion reactions: an assessment of electron correlation effects

MP2 and CAS SCF calculations for CO insertion reactions of the type RMCO → M(COR), R = H, CH₃; M = Mn, Pd⁺ are reported. Non-dynamical correlation appears to be quite important, involving essentially the metal-carbon π bond in the Mn(I) systems and the metal-carbon and metal-hydrogen σ bonds in the Pd(II) systems.     

Theoretical description of the geometric and electronic structures of organic-organic interfaces in organic solar cells: a brief review

We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations.     

(Ph3P)2,Co(CO)2Cl和(dppe-P,P)2CO(CO)+的分子轨道研究

本文对(PH3P)2, Co(CO)2Cl和(dppe-P,P)2CO(CO)+(dppe=Ph2CH2CH2PPh2)五配位C2O对称性模型化合物进行了分轨道研究, 结果表明, 钴的3d轨道很少参与成键, 钴的4s, 4P与配体的S,P轨道通过形式上的二电子三中心键和二电子二中心键的相互作用构成五配位, 此外, 还解释了这两种化合物不同稳定性的原因。     

Mass spectrometry and planetary exploration: A brief review and future projection

Since the inception of mass spectrometry more than a century ago, the field has matured as analytical capabilities have progressed, instrument configurations multiplied, and applications proliferated. Modern systems are able to characterize volatile and nonvolatile sample materials, quantitatively measure abundances of molecular and elemental species with low limits of detection, and determine isotopic compositions with high degrees of precision and accuracy. Consequently, mass spectrometers have a rich history and promising future in planetary exploration. Here, we provide a short review on the development of mass analyzers and supporting subsystems (eg, ionization sources and detector assemblies) that have significant heritage in spaceflight applications, and we introduce a selection of emerging technologies that may enable new and/or augmented mission concepts in the coming decades.     

Theoretical study of I2O

We present high-level density functional calculations (DFT) on the unknown I₂O molecule. The results suggest that the compound may be sufficiently stable for detection and synthesis. Our results also suggest that the DFT method is a reliable and computationally cheap alternative to G2, for estimating thermodynamic properties. The trends in relative stabilities within the HOX and X₂O series are discussed (X=halogen). © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:383–385, 1998     

Theoretical study of ScCO2+

The structure, binding energy, and vibrational frequencies have been determined for ScCO₂⁺. The inserted OSc⁺CO structure in the ¹A′ state is the most stable isomer and lies 43.2 kcal/mol below the ground-state Sc⁺+ CO₂ asymptote. The linear η¹-O Sc⁺(SINGLE BOND)OCO ³Δ state is bound by a charge-quadrupole interaction and has a binding energy of 13.9 kcal/mol. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 523–528, 1997     

Ion scattering from 0.1 keV to 10 MeV: A brief review

Extensive reviews exist for different modes and energy ranges of ion scattering but few articles deal with the similarity of approach between energy ranges. There are a number of aspects of ion scattering which exhibit a gradual change over the energy range from 100eV to 10MeV and this affects the application of the technique, the detection methods and the information which can be derived from the analysis.     

A brief review on miniaturized electrochemiluminescence devices: From fabrication to applications

Miniaturized electrochemiluminescence (ECL) systems are widely recognized as a highly detection, user-friendly, and turnkey strategy to develop point-of-care-testing devices. The ECL sensing approach provides numerous advantages over other methods, including high signal-to-noise ratio and measurement with minimal or no background signal. The ECL signal can be easily controlled by a small external potential while providing high sensitivity and decreased electrode fouling, resulting in the use of ECL-based miniaturized systems for detection and monitoring of different analytes, including DNA and bacteria. In this work, different types of miniaturized ECL systems with various fabrication techniques are reviewed and their application in point-of-care-testing is thoroughly discussed. Furthermore, such ECL platforms have been summarized based on the type of the ECL mechanism, electrodes, range of detection, and limit of detection. Finally, some of the upcoming technological interventions to make such a miniaturized ECL platform amenable for portable and on-field analysis have been discussed.     

A spectral-shift study of the hydrophobic hydration of benzene

A study has been made on the shifts in the spectrum of the S ₁S₀ transition in benzene molecules transferred from low-density vapor to dilute, liquid solutions in order to estimate the geometrical parameter R ^v _1u, characterizing the distribution of the solvent molecules around the solute. The R ^v _1u parameter is a measure of the repulsion between the solution components. Effective radii have been derived for the fluctuation cavities whose existence in the pure solvent is necessary to the dissolution. The free energy, enthalpy, and entropy of the boundary between a solute molecule and the solvent have been derived for aqueous solutions. The energy of the hydrogen bonds in pure water has been estimated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 3, pp. 329–339, May–June, 1987.