A computational investigation of electronic structure as well as ¹⁹F and ²⁹Si chemical shielding tensors in the fluorinated silicon fullerenes Si_nF_n (n¡Ü60)

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• 作者：Maryam Anafcheh ; Reza Ghafouri ; ^{reghafouri@gmail.com}
• 刊名：Physica E
• 出版年：2013
• 出版时间：February, 2013
• 年：2013
• 卷：48
• 期：Complete
• 页码：13-20
• 全文大小：1360 K

文摘

Density functional theory (DFT) calculations are performed to investigate the electronic features of the structures of fluorinated polysilanes Si_nF_n (n=4, 6, 8, 10, 12, 20, 24, 28, 30, 32, 36, 50, and 60). Among all of these fluorinated polysilanes, Si₂₀F₂₀ has the highest binding energy and, thus, stability. The binding energy then shows a very slow (monotonically) decrease as the size of the fluorinated silicon fullerene n¡Ý20 increases which can be related to an increase in fluorine-fluorine repulsion. Following an irregular pattern, the HOMO-LUMO energy gap strongly depends on the size of the cage. On the other hand, ²⁹Si CS parameters detect equivalent electronic environment for silicon atoms within Si_nH_n polysilanes with n¡Ü20 while ²⁹Si NMR pattern indicates a few separated peaks for Si_nH_n polysilanes with n¡Ý20. Seeking correlation between these peaks and local structures around silicon sites, Si_¦Á, Si_¦Â, Si_¦Ã observed in these models shows that ¦Ä_iso(Si_¦Ã)<¦Ä_iso(Si_¦Â) <¦Ä_iso(Si_¦Á). Obtaining similar values (458.8-478.7 ppm) of ¹⁹F calculated chemical shieldings for all the fluorinated polysilanes means the same tendency of the silicon atoms on the surfaces of all cages for contribution to chemical bonding with fluorine atoms.