Infrared spectroscopy and Density Functional Theory of crystalline β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β CL-20) in the region of its C–H stretching vibrations

• The CH stretching vibrations of energetic material β-CL-20 were investigated.
• IR, Raman, Laser Photoacoustics, and Density Functional Theory (DFT) were employed.
• The C–H bond energy of CL-20 was determined experimentally and by DFT.

Molecular vibrational spectroscopy provides a useful tool for material characterization and model verification. We examine the CH stretching fundamental and overtones of energetic material β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β-CL-20) by Raman spectroscopy, Fourier Transform Infrared Spectroscopy, and Laser Photoacoustic Overtone Spectroscopy, and utilize Density Functional Theory to calculate the C–H bond energy of β-CL-20 in a crystal. The spectra reveal four intense and distinct features, whose analysis yields C–H stretching fundamental frequencies and anharmonicity values that range from 3137 to 3170 cm−1 and 53.8 to 58.8 cm−1, respectively. From these data, we estimate an average value of 42,700 cm−1 (5.29 eV) for the C–H bond energy, a value that agrees with our quantum mechanical calculations.

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