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Raman spectra and vibrational properties of FOX-7 under pressure and temperature: First-principles calculations.
- Source :
-
Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy . May2023, Vol. 293, pN.PAG-N.PAG. 1p. - Publication Year :
- 2023
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Abstract
- [Display omitted] • Raman spectra and vibrational properties of five FOX-7 polymorphs were calculated. • Phases α' and β are intermediate phases with transitional properties. • NH2 anti-symmetry-stretching softening under pressure corresponds to H-transfer. FOX-7 (1,1-diamino-2,2-dinitroethene) as one of the widely studied insensitive high explosives exists five polymorphs (α, β, γ, α', ε) whose crystal structures have been determined by XRD (X-rays Diffraction) and which are investigated by a density functional theory (DFT) approach in this work. The calculation results show that the GGA PBE-D2 method can reproduce the experimental crystal structure of FOX-7 polymorphs better. The calculated Raman spectra of FOX-7 polymorphs were compared in detail and fully with the experimental Raman spectra data and it was found that the calculated Raman spectra frequencies have an overall red-shift in middle band (800–1700 cm−1), and that the maximum deviation does not exceed 4 % (The maximum point is the mode of C C in plane bending). The high-temperature phase transform path (α → β → γ) and the high-pressure phase transform path (α → α'→ε) can be well represented in the computational Raman spectra. In addition, crystal structure of ε-FOX-7 was performed up to 70 GPa to probe Raman spectra and vibrational properties. The results showed that the NH 2 Raman shift is jittering with pressure (not smooth compared to other vibrational modes) and NH 2 anti-symmetry-stretching appears red-shifted. The vibration of hydrogen mixes in all of other vibrational modes. This work shows that the dispersion-corrected GGA PBE method can reproduce the experimental structure, vibrational properties and Raman spectra very well. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 13861425
- Volume :
- 293
- Database :
- Academic Search Index
- Journal :
- Spectrochimica Acta Part A: Molecular & Biomolecular Spectroscopy
- Publication Type :
- Academic Journal
- Accession number :
- 162288771
- Full Text :
- https://doi.org/10.1016/j.saa.2023.122489