High-temperature thermal decomposition of iso-octane based on reactive molecular dynamics simulations.

Branched alkanes are the major components of endothermic fuels used for advanced aircrafts. Reactive molecular dynamics (RMD) simulations are carried out to explore the detailed kinetic mechanism for the thermal decomposition of iso-octane widely used as the primary reference fuel of branched alkanes. The RMD calculations indicate that the initial decomposition mechanism of iso-octane is mainly through two pathways: (1) the C - C bond cleavage to produce smaller hydrocarbon radicals and (2) the hydrogen-abstraction reactions by small radicals including •H and •CH.

Investigation on the Thermal Dissociation of Vinyl Nitrite with a Saddle Point Involved.

Hybrid and double-hybrid density functionals are employed to explore the O-NO bond dissociation mechanism of vinyl nitrite (CH=CHONO) into vinoxy (CH=CHO) and nitric monoxide (NO). In contrast to previous investigations, which point out that the O-NO bond dissociation of vinyl nitrite is barrierless, our computational results clearly reveal that a kinetic barrier (first-order saddle point) in the O-NO bond dissociation is involved. Furthermore, a radical-radical adduct is recommended to be present on the dissociation path.

Computational Study of the Reaction of Dimethyl Ether with Nitric Oxide. Mechanism and Kinetic Modeling.

To probe into the autoignition effect of nitric oxide (NO) on the combustion of dimethyl ether (DME), a detailed mechanism study and kinetic modeling for the reaction of DME with NO, which was considered to be very sensitive to the ignition delay time of DME, have been conducted using computational chemical methods. The CCSD(T)/6-311+G(2df,2p)//B2PLYP/TZVP compound method was employed to obtain the potential energy surface along the reaction coordinate, with the geometries, gradients, and force constants of nonstationary points calculated at the B2PLYP/TZVP theoretical level. The temperature-dependent rate coefficients from 200 to 3000 K were calculated using multistructural canonical variational transition-state theory (MS-CVT) with torsional motions and multidimensional tunneling effects included.

Key driving forces of desertification in the Mu Us Desert, China.

The temporal trends and key driving forces of desertification in the Mu Us Desert are representatives of most arid regions of Asia with a high risk of desertification. We analyzed the significance of Aeolian transport on desertification in the Mu Us Desert by field investigations, sampling, wind tunnel experiments, particle size and nutrient measurements, and statistics on aeolian transport potentials. The results showed that high intensities of aeolian processes may result in low differences in aeolian transport despite differences in the underlying sediments.