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The ammonium nitrate and its mechanism of decomposition in the gas phase: a theoretical study and a DFT benchmark.

Authors
  • Cagnina, Stefania
  • Rotureau, Patricia
  • Fayet, Guillaume
  • Adamo, Carlo
  • Guillaume FAYET
Type
Published Article
Journal
Physical Chemistry Chemical Physics
Publisher
The Royal Society of Chemistry
Publication Date
Jul 13, 2013
Volume
15
Issue
26
Pages
10849–10858
Identifiers
DOI: 10.1039/c3cp50368b
PMID: 23698194
Source
Medline
License
Unknown

Abstract

The decomposition mechanism of ammonium nitrate in the gas phase was investigated and fully characterized by means of CBS-QB3 calculations. Five reaction channels were identified, leading to the formation of products (N2, H2O, O2, OH, HNO, NO3) found in the experimental works. The identified mechanism well underlines the origin of the chemical hazard of ammonium nitrate which is related to the exothermicity of the lowest decomposition channels. Furthermore, the high barrier to overcome in the rate determining step well explained the fact that the reaction is not usually spontaneous and requires a significant external stimulus for its onset. An accurate DFT benchmark study was then conducted to determine the most suitable exchange-correlation functional to accurately describe the reaction profile both in terms of structures and thermochemistry. This evaluation supports the use of the M06-2X functional as the best option for the study of ammonium nitrate decomposition and related reactions. Indeed, this level of theory provided the lowest deviations with respect to CBS-QB3 reference values, outperforming functionals especially developed for reaction kinetics.

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