Density functional calculations as a tool for the characterization of ultrahin organic films: synthesis and spectroscopic characterization of RDX 'monolayers' on glass substrates

摘要

Density functional theory calculations (DFT), Raman and atomic force microscopy (AFM) were employed to study the surface chemistry of ultra thin films of RDX on glass substrates. The preparation method played a major role in the morphology of the RDX films. Dispersed particles (500 nm) and larger (25 μm) crystals were observed in AFM. The vibrational fingerprint of RDX indicates the presence of β and α RDX phases. DFT calculations predict the RDX molecule to have all three NO_2 groups in axial position with respect to a distorted triazine ring. The agreement between calculated and measured Raman frequencies was excellent. Measured Raman intensities and depolarization ratios were found to lie between 0.61 and 0.75, indicating that the vibrational modes have low symmetry.