Terahertz spectroscopy of 2,4,6-trinitrotoluene molecular solids from first principles
نویسندگان
چکیده
We present a computational analysis of the terahertz spectra of the monoclinic and the orthorhombic polymorphs of 2,4,6-trinitrotoluene. Very good agreement with experimental data is found when using density functional theory that includes Tkatchenko-Scheffler pair-wise dispersion interactions. Furthermore, we show that for these polymorphs the theoretical results are only weakly affected by many-body dispersion contributions. The absence of dispersion interactions, however, causes sizable shifts in vibrational frequencies and directly affects the spatial character of the vibrational modes. Mode assignment allows for a distinction between the contributions of the monoclinic and orthorhombic polymorphs and shows that modes in the range from 0 to ca. 3.3 THz comprise both inter- and intramolecular vibrations, with the former dominating below ca. 1.5 THz. We also find that intramolecular contributions primarily involve the nitro and methyl groups. Finally, we present a prediction for the terahertz spectrum of 1,3,5-trinitrobenzene, showing that a modest chemical change leads to a markedly different terahertz spectrum.
منابع مشابه
Wideband terahertz spectroscopy of explosives
Time-domain terahertz spectroscopy (TDTS) has been shown to be a promising tool in detection of explosives and explosive related compounds. To date, TDTS for many explosives has been limited to spectral regions <3 THz. With recent improvements in emitters and sensors of THz radiation, we report the THz absorption spectra over an extended frequency band from 0.5 to 6 THz for four explosives: RDX...
متن کاملTerahertz study of trichloroanisole by time-domain spectroscopy
The THz transmission spectra of three trichloroanisole (TCA) compounds (2,3,4-TCA, 2,4,6-TCA and 2,5,6TCA) are measured using terahertz time-domain spectroscopy (THz-TDS). The spectrum of 2,4,6-TCA in the solid phase displays several discrete absorption peaks over frequency range from 0.1 to 1.5 THz, with significant peaks observed at 0.6, 0.95 and 1.2 THz. A weak absorption peak is observed ne...
متن کاملScreening Effective Factors in Slurry Phase Bioremediation of 2,4,6-Trinitrotoluene (TNT) Contaminated Soil
متن کامل
High Resolution Waveguide Terahertz Time-Domain Spectroscopy
Terahertz time-domain spectroscopy accesses the frequency range between 100 GHz and 5 THz by using the coherent generation and detection based on femtosecond laser sources. On the way to obtain fingerprint absorption spectra of molecular solids, terahertz waveguides have proven to be a valuable tool to extend the results to narrow and high resolution linewidths of crystalline solids. We will di...
متن کاملDirect measurement of molecular mobility and crystallisation of amorphous pharmaceuticals using terahertz spectroscopy.
Despite much effort in the area, no comprehensive understanding of the formation and behaviour of amorphous solids has yet been achieved. This severely limits the industrial application of such materials, including drug delivery where, in principle, amorphous solids have demonstrated their great usefulness in increasing the bioavailability of poorly aqueous soluble active pharmaceutical ingredi...
متن کامل