density functional theory; THz spectroscopyAbstract 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
Résumé :
[en] 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.
Disciplines :
Physique
Auteur, co-auteur :
Azuri, Ido; Weizmann Institute of Science, Rehovoth 76100, Israel > Department of Materials and Interfaces,
Hirsch, Anna; Weizmann Institute of Science, Rehovoth 76100, Israel
Reilly, Anthony; School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland
TKATCHENKO, Alexandre ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Kendler, Shai
Hod, Oded
Kronik, Leeor
Co-auteurs externes :
yes
Langue du document :
Anglais
Titre :
Terahertz spectroscopy of 2,4,6-trinitrotoluene molecular solids from first principles
