Ab Initio and Nonlocal Density Functional Study of 1,3,5-trinitro-s-triazine (RDX) Conformers
Abstract
Geometry optimizations and normal-mode analyses of three conformers of 1,3,5-trinitro-s-triazine (RDX) are performed using second-order Moller-Plesset (MP2) and nonlocal density functional theory (DFT) methods. The density function used in this study is B3LYP. The three conformers of RDX are distinguished mainly by the arrangement of the nitro groups relative to the ring atoms of the RDX molecule. NO2 groups arranged in either pseudo-equatorial or axial positions are denoted with (E) or (A), respectively. The axial-axial-equitorial (AAE) conformer has Cs symmetry and is the structure in the room-temperature-stable crystal (alpha-RDX). The axial-axial-axial (AAA) and equitorial-equitorial-equitorial (EEE) conformers have C3v symmetry, a symmetry consistent with vapor and beta-solid infrared (IR) spectra. The AAE and AAA conformers are studied at the MP2/6-31G*, B3LYP/6-31G*, and B3LYP16-311+G** levels, and the EEE conformer is studied using the B3LYP density function and the 6-31G* and 6-311+G** basis sets. The geometric parameters and IR spectra of the AAA conformer are in good agreement with experimental gas-phase and beta-solid data, supporting the hypotheses derived from experiment that the AAA structure is the most probable conformer in vapor-phase and beta-solid RDX. The B3LYP/6-311+G** structures and simulated IR spectra are in closest agreement with experimental data. The MP2/6-31G* structures and spectra are in poorest agreement with experiment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1998
- Accession Number
- ADA335728
Entities
People
- Betsy M. Rice
- Cary F. Chabalowski
Organizations
- United States Army Research Laboratory