Note: Chevron, Energy Technology Company, 100 Chevron Way, Richmond, California 94802-0627 Reference EPFL-ARTICLE-200588doi:10.1021/cr8002642 URL: http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/cr8002642 URL: http://pubs.acs.org/doi/pdfplus/10.1021/cr8002642 Record created on 2014-08-14, modified on 2017-05-12

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Quantum mechanically determined electrostatic potentials for isosurfaces of electron density of a variety of CHNO explosive molecules are analyzed to identify features that are indicative of sensit...

A quantum mechanical investigation of the relation between impact sensitivity and the charge distribution in energetic molecules

Tautomeric equilibria in relation to pi-electron delocalization.

The heats of formation (HOF) for 49 tetrazole derivatives are calculated with the density functional theory (DFT) B3LYP method by means of designed isodemic and isogyric reactions. The average abso...

Studies on Heats of Formation for Tetrazole Derivatives with Density Functional Theory B3LYP Method

The heats of formation (HOFs) for a series of 1,2,4,5-tetrazine derivatives were calculated by using density functional theory (DFT), Hartree Fork (HF), and Moller−Plesset (MP2) as well as semiempirical methods. The effects of different basis bets on HOFs were also considered. Our results show that the −CN or −N3 group plays a very important role in increasing the HOF values of the 1,2,4,5-tetrazine derivatives. An analysis of the bond dissociation energies for the weakest bonds indicates that substitutions of the −N3, −NH2, −CN, −OH, or −Cl group are favorable for enhancing the thermal stability of 1,2,4,5-tetrazine, but the −NHNH2, −NHNO2, −NO2, −NF2, or −COOH group produces opposite effects. The calculated detonation velocities and pressures indicate that the −NF2 or −NO2 group is very helpful for enhancing the detonation performance for the derivatives, but the case is quite the contrary for the −CN, −NH2, or −OH group. Considered the detonation performance and thermal stability, three derivatives may...

Molecular design of 1,2,4,5-tetrazine-based high-energy density materials.

The UHF-SCF-AM1 method has been employed to study the pyrolysis mechanism and impact sensitivity of nitro derivatives of benzene. Potential energy curves, transition states and activation energies of seven pyrolysis initiation reactions (homolysis of CNO2 bond into radicals) have been obtained here first. The molecular geometries of reactants, transition states and products of the seven reactions were fully optimized. It is found that there is a good linear relationship between the activation energies and bond orders of the weakest bond CNO2 in the molecule of each reactant. The linear correlation coefficient is 0.996. This result gives “the principle of the smallest bond order” powerful support and shows that the activation energy can also be used as a dynamic criterion of impact sensitivity.

Theoretical study on pyrolysis and sensitivity of energetic compounds. (2) Nitro derivatives of benzene

The derivatives of 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. Detonation properties are evaluated using the modified Kamlet−Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between the density, detonation velocity, detonation pressure, and number of nitro, amino, and hydroxy groups. The thermal stability and pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies at the unrestricted B3LYP/6-31G* level. For the nitro and amino derivatives of HNS, the C−NO2 bond is a trigger bond during the thermolysis initiation process, while for hydroxy derivatives, it is started from the isomerization reaction of the hydrogen transfer in the O−H bond. According to the quantitative standard of energetics and stability, as high-energy density compounds, 2,2′,3,3′,4,4′,5,6,6′-nonanitrostilbene ...

Theoretical investigation on structures, densities, detonation properties, and the pyrolysis mechanism of the derivatives of HNS.

By using both DV-Xα and EH-CO methods, the calculation studies of the structure-property relationships of a series of metal azides, of their clusters' electronic structures in ground and excited states, of their systems with cation vacancy and the doped Pb(N3)2, as well as their crystal band structures have been conducted. The results show that the sensitivity of ionic-type metal azides varies with the degree of difficulty of electronic transition of the losing charge on N3. A metal azide with cation vacancies has a greater sensitivity than the perfect one. When doped with monovalent metal ions, lead azide's sensitivity increased; when with trivalent ones, its sensitivity decreased; when with divalent ones, little of it changed. Compared with heavy metal azides. an alkali metal azide has a larger band gap, a smaller band width and a greater transition energy of frontier electron with a smaller amount of losing charge on N3, and thus has lower sensitivity and conductivity than heavy metal azides.

Banding and electronic structures of metal azides——Sensitivity and conductivity

Five polymer bonded explosives (PBXs) with the base explosive e-CL-20 (hexanitrohexaazaisowurtzitane), the most important high energy density compound (HEDC), and five polymer binders (Estane 5703, GAP, HTPB, PEG, and F2314) were constructed. Molecular dynamics (MD) method was employed to investigate their binding energies (E
 bind), compatibility, safety, mechanical properties, and energetic properties. The information and rules were reported for choosing better binders and guiding formulation design of high energy density material (HEDM). According to the calculated binding energies, the ordering of compatibility and stability of the five PBXs was predicted as e-CL-20/PEG > e-CL-20/Estane5703 ≈ e-CL-20/GAP > e-CL-20/HTPB > e-CL-20/F2314. By pair correlation function g(r) analyses, hydrogen bonds and vdw are found to be the main interactions between the two components. The elasticity and isotropy of PBXs based e-CL-20 can be obviously improved more than pure e-CL-20 crystal. It is not by changing the molecular structures of e-CL-20 for each binder to affect the sensitivity. The safety and energetic properties of these PBXs are mainly influenced by the thermal capability (C°p) and density (ρ) of binders, respectively.

Molecular dynamics simulations on the structures and properties of ε-CL-20-based PBXs ——Primary theoretical studies on HEDM formulation design

The relative orders of impact sensitivity of tetrazole derivatives and their metal salts are investigated by examining the activation energy for forming azide in the process of thermal decomposition based on PM3-SCF-MO calculations. It is found that there is a parallel relationship between the activation energy and the sensitivity and a good linear relationship between the experimental impact sensitivity of metal salts of tetrazole and the reaction activation energy. It is shown that treating the metal salts of the tetrazole derivatives as the metal derivatives of tetrazole is meaningful.

Xiao Heming

Papers

Theoretical study on pyrolysis and sensitivity of energetic compounds. (2) Nitro derivatives of benzene

Theoretical investigation on structures, densities, detonation properties, and the pyrolysis mechanism of the derivatives of HNS.

Banding and electronic structures of metal azides——Sensitivity and conductivity

Molecular dynamics simulations on the structures and properties of ε-CL-20-based PBXs ——Primary theoretical studies on HEDM formulation design

Theoretical investigation on the impact sensitivity of tetrazole derivatives and their metal salts