Science and Technology of Energetic Materials

Vol.66, No.3 (2005)


High pressure phase of RDX
Naoyuki Goto, Hiroshi Yamawaki, Kunihiko Wakabayashi, Yoshio Nakayama, Masatake Yoshida, and Mitsuo Koshi


We have studied behaviors of one of high sensitive explosives, RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), under static ultrahigh pressures (up to 50 GPa) generated by a diamond anvil cell (DAC) with FT-IR spectroscopy. Quantum chemical calculations using a density functional theory (DFT) with the Becke3-Lee-Yang-Parr (B3LYP) hybrid density functional and 6-31G(d), 6-311+G(d,p), and 6-311++G(3df,3pd) basis sets were also performed on six conformers of RDX. The molecular structure of high pressure phase of RDX (γ-RDX) was discussed by comparing the shape of the FT-IR spectra with the shape obtained by DFT calculations. Potential energy surface (PES) calculations were performed to discuss the validity of the isomerization. Molecular dynamics (MD) simulations were performed to discuss the pressure dependence of the IR frequencies.

High pressure FT-IR spectra did not show the degenerated structure that is characteristics of C3v point group. Comparing the observed FT-IR spectra, IR frequencies obtained by DFT, and the pressure dependence of the IR frequencies obtained by MD simulations, the high pressure structure of RDX was suggested to be of the AEE type, in which one of the NO2 bond angles to the six-membered ring is axial, while the others are equatorial. PES calculations also supported this conclusion.

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