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8316663 
Journal Article 
Carbon K edge structures of molecular crystals from first-principles: A comparison between phenanthrene and anthracene 
Nejatipour, H; Dadsetani, M 
2018 
Isfahan University of Technology 
18 
3 
41-51 
English 
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 s structure has a red shift. The ELNES spectrum of crystalline phenanthrene includes electron transition of 1s carbon orbital to p* and s* states. In anthracene, the first two intense features have contributions of p* 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. © 2018, Isfahan University of Technology. All rights reserved. 
Anthracene; Density functional theory; ELNES; Organic molecular crystals; Phenanthrene