High-level ab initio and density functional theory evaluation of combustion reaction energetics: NO{sub 2} and HONO elimination from dimethylnitramine
Accurate numerical models for combustion of high-energy (HE) materials have safety and educational benefits and are viable alternatives to dangerous experimental tests. Indeed, modeling an explosion is a challenging problem that requires extensive atomic-scale information such as detailed chemical reaction mechanisms with associated thermodynamic and kinetic parameters, many of which are still not known. Understanding the decomposition of HE molecules is a key element in the simulation of explosions and combustion of propellants. Dimethylnitramine (DMNA) is used as a model system for investigating accurate and efficient electronic structure methods for nitramines. Critical points on the potential energy surfaces of DMNA, CH{sub 3}NCH{sub 3}, CH{sub 3}NCH{sub 2}, NO{sub 2}, HONO, and the transition state to HONO elimination were located through geometry optimizations using the B1LYP, B3LYP, MPW1PW91, and BH and HLYP density functional methods, in addition to MP2, G2(MP2), and QCISD ab initio theories using the cc-pVDZ basis set. For cost-effective determination of nitramine reaction energetics, highly correlated single-point calculations at DFT geometries are recommended. The best estimated reaction enthalpies for N-N bond scission and HONO elimination are 41.6 and {minus}0.9 kcal/mol, respectively, determined at the QCISD(T)//QCISD level of theory. These numbers can be reproduced to within 1.3 kcal/mol for the N-N bond and to within 0.5 kcal/mol for the HONO reaction by calculating QCISD(T) energies at B1LYP geometries, thus saving considerable computational cost without sacrificing accuracy. Using the same strategy, the transition state energy for HONO elimination can be modeled to within 0.1 kcal/mol of the QCISD(T)//QCISD result.
- Research Organization:
- Univ. of Utah, Salt Lake City, UT (US)
- Sponsoring Organization:
- US Department of Energy
- OSTI ID:
- 20003217
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 44 Vol. 103; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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