Carbon K edge structures of molecular crystals from first-principles: A comparison between phenanthrene and anthracene
By means of ab-initio calculations on the basis of the FPLAPW method, we compared the energy loss near edge structure (ELNES) of carbon K edges in crystalline phenanthrene and its isomer, anthracene. In these two organic compounds, different non-equivalent carbon atoms can result in distinct K edge...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Isfahan University of Technology
2018-12-01
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| Series: | Iranian Journal of Physics Research |
| Subjects: | |
| Online Access: | http://ijpr.iut.ac.ir/browse.php?a_code=A-10-293-1&slc_lang=en&sid=1 |
| Summary: | By means of ab-initio calculations on the basis of the FPLAPW method, we compared the energy loss near edge structure (ELNES) of carbon K edges in crystalline phenanthrene and its isomer, anthracene. In these two organic compounds, different non-equivalent carbon atoms can result in distinct K edge spectra due to the different carbon-carbon bond lengths, as a characteristic behavior of the molecular crystals. The smaller bond lengths push the ELNES features to the higher energies. In anthracene, the energy position of the edge-onset appears at lower energies due to its smaller electronic band gap. At the onset of the C K edge of anthracene, the strong splitting of the π* peak into two peaks is observable. Compared to the C K edge in anthracene, due to the slightly larger C–C bond length in phenanthrene, the peak position of the main σ structure has a red shift. The ELNES spectrum of crystalline phenanthrene includes electron transition of 1s carbon orbital to π* and σ* states. In anthracene, the first two intense features have contributions of π* orbitals. Consideration of the core-hole approximation by means of super-cells and the collection of semi-angles at magic value are essential to obtain reasonable ELNES spectra. |
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| ISSN: | 1682-6957 2345-3664 |