Publication
Reference
Ennis C., Auchettl R., Appadoo D. R. T., Robertson E. G. (2018). The prediction of far-infrared spectra for planetary nitrile ices using periodic density functional theory with comparison to thin film experiments. Phys. Chem. Chem. Phys., 20, 23593 - 23605.
Names
  • C. Ennis
  • R. Auchettl
  • D. R. T. Appadoo
  • E. G. Robertson
Article and keywords
Title
The prediction of far-infrared spectra for planetary nitrile ices using periodic density functional theory with comparison to thin film experiments
Abstract
Future spacecraft missions to planetary systems, Trans-Neptunian objects, and cometary bodies could implement far-infrared surveys to confirm the presence of condensed-phase species via their unique lattice features. For composite molecular ices of astrophysical significance, laboratory reference spectra are required to provide absorption coefficients used to quantify solid-state abundances. However, due to strong intermolecular interactions in polar ice systems, laboratory data of mixed-phase ices are difficult to interpret. In this study we have applied periodic density functional theory code to model bulk molecular crystals. This method allows for more accurate simulation of thin-film spectra than approaches simulating small clusters. For this proof-of-principle study on a series of pure nitrile ices of planetary interest, our simulated far-infrared spectra show excellent agreement to data from thin film studies performed at the Australian Synchrotron (crystalline acetonitrile and propionitrile) and to previously published spectra (hydrogen cyanide, acrylonitrile, cyanoacetylene, and cyanogen). The combined theoretical and experimental approach has provided a new explanation for the asymmetric profile of the hydrogen cyanide lattice feature and a more systematic assignment of nitrile ice absorption bands to low-frequency lattice modes. We nominate prominent absorption features for the detection of crystalline nitrile carriers located on planetary surfaces.
Keywords
spectroscopy, absorbance spectra, simulated spectra, data analysis, band position, band vibration mode, mid-IR, far-IR, crystalline, molecular solid, nitrile, CH3CN, C2H5CN, CH2CHCN, HCN, C2N2, HC3N, acetonitrile, propionitrile, acrylonitrile, hydrogen cyanide, cyanogen, cyanoacetylene, Titan
Content
spectral data, experimental physics, theoretical physics
Year
2018
Journal
Physical Chemistry Chemical Physics
Volume
20
Number
36
Pages
23593 - 23605
Document type
article
Publication state
published
Doi
10.1039/C8CP04219E
Identifiers