Title

Direct Dynamics Simulation of the Activation and Dissociation of 1,5-Dinitrobiuret (HDNB)

Abstract

Certain room-temperature ionic liquids exhibit hypergolic activity as liquid bipropellants. Understanding the chemical pathways and reaction mechanisms associated with hypergolic ignition is important for designing new fuels. It has been proposed ( J. Phys. Chem. A 2008, 112, 7816) that an important ignition step for the hypergolic ionic liquid bipropellant system of dicyanamide/nitric acid is the activation and dissociation of the 1,5-dinitrobiuret anion DNB-. For the work reported here, a quasiclassical direct dynamics simulation, at the DFT/M05-2X level of theory, was performed to model H+ + DNB- association and the ensuing unimolecular decomposition of HDNB. This association step is 324 kcal/mol exothermic, and the most probable collision event is for H+ to directly scatter off of DNB-, without sufficient energy transfer to DNB- for H+ to associate and form a highly vibrationally excited HDNB molecule. Approximately 1/3 of the trajectories do form HDNB, which decomposes by eight different reaction paths and whose unimolecular dynamics is highly nonstatistical. Some of these paths are the same as those found in a direct dynamics simulation of the high-temperature thermal decomposition of HDNB ( J. Phys. Chem. A 2011, 115, 8064), for a similar total energy.

Document Type

Article

DOI

https://doi.org/10.1021/jp5002622

Keywords

energy, molecular structure, molecular dynamics simulations, computational chemistry, molecules

Publication Date

2014

Recommended Citation

Sun, Rui, Matthew R. Siebert, Lai Xu, Steven D. Chambreau, Ghanshyan L. Vaghjiani, Hans Lischka, Jianbo Liu, and William L. Hase. "Direct dynamics simulation of the activation and dissociation of 1, 5-dinitrobiuret (HDNB)." The Journal of Physical Chemistry A 118, no. 12 (2014): 2228-2236.

Journal Title

The Journal of Physical Chemistry A

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