Simulation nitromethane

Early Chemistry in Hot and Dense Nitromethane Molecular Dynamics Simulations. 

The concentration of nitromethane in automobile exhaust using nine hydrocarbon test fuels under simulated driving conditions ranged from < 0.8 to 5.0 ppm (Seizinger Dimitriades, 1972). 

Van Tamelen has examined extensively the cyclization of monoepoxide-polyolefins (94). For example, he found (95) that the treatment of racemic epoxide 247 with SnCl in nitromethane provided a major product (35% yield) which was identified as the racemic tetracycle 248. This represents an over all, close simulation of the squalene tetracyclic triterpene bioconversion (except for optical activity). 

Although the mechanism is far from completely determined (which is not surprising given its complexity), there are sufficient details to invite attempts to simulate the chemistry of this prototypical energetic material. Its size permits accurate ab initio calculations to determine the potential energy surface of the reactions in the proposed mechanism many of the secondary reactions are of interest in other combustion systems and have been studied by various experimental and theoretical approaches. Even a cursory discussion of the theoretical studies of secondary reactions involved in the decomposition of nitromethane is beyond the scope of this chapter we limit the discussion to the initial decomposition steps. 

Other flexible molecular models of nitromethane were developed by Politzer et al. [131,132]. In these, parameters for classical force fields that describe intramolecular and intermolecular motion are adjusted at intervals during a condensed phase molecular dynamics simulation until experimental properties are reproduced. In their first study, these authors used quantum-mechanically calculated force constants for an isolated nitromethane molecule for the intramolecular interaction terms. Coulombic interactions were treated using partial charges centered on the nuclei of the atoms, and determined from fitting to the quantum mechanical electrostatic potential surrounding the molecule. After an equilibration trajectory in which the final temperature had been scaled to the desired value (300 K), a cluster of nine molecules was selected for a density function calculation from which... 

The first sections of this chapter are devoted to a description of the method and practical details for its implementation and utilization. Subsequent sections extend the method to the detection and simulation of double shock waves, which are ubiquitous in condensed matter. Example applications are presented for a Lennard-Jones atomic potential system (which can provide a description of solid Argon), an empirical potential model of crystalline silicon, and a tight-binding atomic potential for the chemically reactive explosive nitromethane (CH3NO2). 

The second event in simulation C is a second proton transfer, observed at 60 fs, and is due to an intramolecular 0-H attraction. The fast vibrations of the methyl group induce an umbrella inversion type motion that, along with a stretch in a N-O bond, leads to the hydrogen transfer from the methyl to the nitro group. This reaction yields the aci acid form of nitromethane. The process of bond rearrangement is illustrated as ... 

To simulate the effect of unifonn strain on solid nitromethane, the initial lattice parameters were successively decreased by keeping their ratio fixed. The pressure P is estimated by using the low-temperature formula P = dE, , / dV. For hydrostatic compression up to 50% of the original volume Vo, the pressure rises to about 50 GPa, while the HOMO-LUMO gap dropped by 0.6 eV, i.e., by 13% of its original value. This compression results in a simultaneous increase of the HOMO and the LUMO energies, while the decrease of the HOMO-LUMO gap is almost monotonic in the volume strain, as depicted in Fig.2. The change induced in the band gap by very high hydrostatic compression is shown in Fig.3 for strain equal up to 70%. 

Zhao T, Yu C, Han L et al (1994) Experiments and numerical simulations on the difftaction of detonation waves in nitromethane. Explos Shock Waves 14(2) 169-174... 

It has already been mentioned that nitromethane (NM) is very frequently used as a model EM for MO calculations and simulations of various processes connected with initiation reactivity of EMs. Therefore, from the point-of-view of initiation by shock wave, it is given separate attention here. 

Tubular module elements were developed for the above purpose. The preparation of the tubular membranes and the module elements were basically the same as those described earlier. The best results were obtained with SPPO of lEC 1.8 cast onto seamless polysulfone substrate from a nitromethane/methanol/butanol solvent mixture. The tubular module elements were tested under 600 psig for 700 hours at 165 to 170 °F wash water simulating 87 % water recovery. Flux after about 100 hours ranged from 15 to 25 gsfd with salt rejection of 90 to 96 % and soap rejection of 98 %. The flux increased with increasing operation time with practically no change in rejection. After 500 hours of operation a flux of 35 gsfd was achieved. 

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