Department of Physics, University of Patras, GR-26500 Patras, Greece.
J Chem Phys. 2011 Mar 7;134(9):094312. doi: 10.1063/1.3557680.
It is predicted by accurate density functional and coupled-cluster theory that planar Si(5)C and Si(5)C rings can be stabilized by flat pentacoordinate carbon-silicon bonds. The energy difference of the Si(5)C dianion from the lowest energy three-dimensional isomer is about 12.2 kcal∕mol at the level of the density functional theory using the Becke 3-parameter (exchange), Lee, Yang and Parr functional, and the triple-ζ doubly polarized basis sets. Stable composite Si(5)C structures are formed either as nanowheels with axial C-C bonds of 1.51 Å or as isoenergetic pentagonal graphiticlike layers with double C-C distance (3.02 Å) and almost double aromaticity index, based on nucleus independent chemical shifts. Both of these structures are at least 12 kcal∕mol lower in energy than the lowest energy Si(10)C(2) structure reported in the literature, but about 5 kcal∕mol higher than the lowest energy structure found here.
准确的密度泛函和耦合簇理论预测，平面Si(5)C和Si(5)C环可以通过平面五配位硅-碳键稳定。在密度泛函理论水平上，使用 Becke 3-参数（交换）、Lee、Yang 和 Parr 泛函和三重ζ双极化基组，Si(5)C二负离子的最低能量三维异构体的能量差约为 12.2 kcal/mol。基于核独立化学位移，稳定的复合Si(5)C结构形成轴向 C-C 键为 1.51 Å 的纳米轮，或者形成等能量的五边形石墨状层，具有两倍的 C-C 距离（3.02 Å）和几乎两倍的芳构性指数。这两种结构的能量都比文献中报道的最低能量 Si(10)C(2)结构低至少 12 kcal/mol，但比这里发现的最低能量结构高约 5 kcal/mol。
