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Title: Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. A computational approach to the prediction of the heats of formation (ΔHf°’s) of solid-state energetic salts from electronic structure and volume-based thermodynamics (VBT) calculations is described. The method uses as its starting point reliable ΔHf°’s for energetic precursor molecules and ions. The ΔHf°’s of more complex energetics species such as substituted imidazole, 1,2,4-triazole, and tetrazole molecules and ions containing amino, azido, and nitro (including methyl) substituents are calculated using an isodesmic approach at the MP2/complete basis set level. On the basis of comparisons to experimental data for neutral analogues, this isodesmic approach is accurate to <3 kcal/mol for the predicted cation and anion ΔHf°’s. The ΔHf°’s of the energetic salts in the solid state are derived from lattice energy (UL) calculations using a VBT approach. Improved values for the ∝ and β parameters of 19.9 (kcal nm)/mol and 37.6 kcal/mol for the UL equation were obtained on the basis of comparisons to experimental UL’s for a series of 23 saltsmore » containing ammonium, alkylammonium, and hydrazinium cations. The total volumes are adjusted to account for differences between predicted and experimental total volumes due to different shapes of the ions (flat vs spherical). The predicted ΔHf°’s of the energetic salts are estimated to have error bars of 6-7 kcal/mol, on the basis of comparisons to established experimental ΔHf°’s of a subset of the salts studied. Energetic salts with the highest positive ΔHf°’s are predicted for azido-containing cations, coupled with heterocyclic anions containing nitro substituents. The substitution of functional groups on carbon versus nitrogen atoms of the heterocyclic cations has interesting stabilization and destabilization effects, respectively.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
921378
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B, 111(18):4788-4800; Journal Volume: 111; Journal Issue: 18
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IMIDAZOLES; TRIAZOLES; TETRAZOLES; FORMATION HEAT; AZIDO COMPOUNDS; NITRO COMPOUNDS; SALTS; Environmental Molecular Sciences Laboratory

Citation Formats

Gutowski, Keith E, Rogers, Robin D, and Dixon, David A. Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.. United States: N. p., 2007. Web. doi:10.1021/jp066420d.
Gutowski, Keith E, Rogers, Robin D, & Dixon, David A. Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.. United States. doi:10.1021/jp066420d.
Gutowski, Keith E, Rogers, Robin D, and Dixon, David A. Thu . "Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.". United States. doi:10.1021/jp066420d.
@article{osti_921378,
title = {Accurate Thermochemical Properties for Energetic Materials Applications. II. Heats of Formation of Imidazolium-, 1,2,4-Triazolium-, and Tetrazolium-Based Energetic Salts fromIsodesmic and Lattice Energy Calculations.},
author = {Gutowski, Keith E and Rogers, Robin D and Dixon, David A},
abstractNote = {The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. A computational approach to the prediction of the heats of formation (ΔHf°’s) of solid-state energetic salts from electronic structure and volume-based thermodynamics (VBT) calculations is described. The method uses as its starting point reliable ΔHf°’s for energetic precursor molecules and ions. The ΔHf°’s of more complex energetics species such as substituted imidazole, 1,2,4-triazole, and tetrazole molecules and ions containing amino, azido, and nitro (including methyl) substituents are calculated using an isodesmic approach at the MP2/complete basis set level. On the basis of comparisons to experimental data for neutral analogues, this isodesmic approach is accurate to <3 kcal/mol for the predicted cation and anion ΔHf°’s. The ΔHf°’s of the energetic salts in the solid state are derived from lattice energy (UL) calculations using a VBT approach. Improved values for the ∝ and β parameters of 19.9 (kcal nm)/mol and 37.6 kcal/mol for the UL equation were obtained on the basis of comparisons to experimental UL’s for a series of 23 salts containing ammonium, alkylammonium, and hydrazinium cations. The total volumes are adjusted to account for differences between predicted and experimental total volumes due to different shapes of the ions (flat vs spherical). The predicted ΔHf°’s of the energetic salts are estimated to have error bars of 6-7 kcal/mol, on the basis of comparisons to established experimental ΔHf°’s of a subset of the salts studied. Energetic salts with the highest positive ΔHf°’s are predicted for azido-containing cations, coupled with heterocyclic anions containing nitro substituents. The substitution of functional groups on carbon versus nitrogen atoms of the heterocyclic cations has interesting stabilization and destabilization effects, respectively.},
doi = {10.1021/jp066420d},
journal = {Journal of Physical Chemistry B, 111(18):4788-4800},
number = 18,
volume = 111,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}