Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

Resonance raman spectra of TNT and RDX using vibronic theory, excited-state gradient, and complex polarizability approximations

UNSPECIFIED (2012) Resonance raman spectra of TNT and RDX using vibronic theory, excited-state gradient, and complex polarizability approximations. Journal of Physical Chemistry A, 116 (30). 7862 - 7872. ISSN 1089-5639

[img] Plain Text (licence)
Available under License : See the attached license file.

Download (1kB)

Abstract

Geometries, UV absorption bands, and resonance Raman (RR) cross sections of TNT and RDX are investigated using density functional theory (DFT) in conjunction with the Coulomb attenuated B3LYP exchange-correlation functional. The absorption and RR spectra are determined with use of vibronic (VB) theory, excited-state gradient, and complex polarizability (CPP) approximations. We examined low-energy isomers (two for TNT and four for RDX) whose energies differ by less than 1 kcal/mol, such that they would appreciably be populated at room temperature. The two TNT isomers differ by an internal rotation of the methyl group, while the four conformers of RDX differ by the arrangements of the nitro group relative to the ring. Our theoretical optical properties of the TNT and RDX isomers are in excellent agreement with experimental and recent CCSD-EOM results, respectively. For the two TNT isomers, the ultraviolet RR (UVRR) spectra are similar and in good agreement with recently measured experimental results. Additionally, the UVRR spectra computed using the excited-state and CPP approaches compare favorably with the VB theory results. On the other hand, the RR spectra of the RDX conformers differ from one another, reflecting the importance of the positioning of the NO 2 groups with respect to the ring. In the gas phase or in solution, RDX would give a spectrum associated with a conformationally averaged structure. It is encouraging that the computed spectra of the conformers show similarities to recent measured RDX spectra in acetonitrile solution, and reproduce the 10-fold decrease in the absolute Raman cross sections of RDX compared to TNT for the observed 229 nm excitation. We show that in TNT and RDX vibrational bands that couple to NO 2 or the ring are particularly resonance enhanced. Finally, the computed RDX spectra of the conformers present a benchmark for understanding the RR spectra of the solid-phase polymorphs of RDX. © 2012 American Chemical Society.


Share

Citation/Export:
Social Networking:
Share |

Details

Item Type: Article
Status: Published
Date: 2 August 2012
Date Type: Publication
Journal or Publication Title: Journal of Physical Chemistry A
Volume: 116
Number: 30
Page Range: 7862 - 7872
DOI or Unique Handle: 10.1021/jp303920c
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 1089-5639
PubMed ID: 22770527
Date Deposited: 14 Feb 2013 21:16
Last Modified: 05 Jan 2019 15:59
URI: http://d-scholarship.pitt.edu/id/eprint/17321

Metrics

Monthly Views for the past 3 years

Plum Analytics

Altmetric.com


Actions (login required)

View Item View Item