Competition between Huckel's Rule and Jahn-Teller Distortion in Small Carbon Rings: A Quantum Monte Carlo Study
Competition between Huckel's Rule and Jahn-Teller Distortion in Small Carbon Rings: A Quantum Monte Carlo Study
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DOI：
10.1021/acs.jpca.0c02577
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发表时间：
2020-05-07
影响因子：
2.9
通讯作者：
Kwon, Yongkyung
中科院分区：
文献类型：
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作者：
Hong, Iuegyun;Ahn, Jeonghwan;Kwon, Yongkyung
用扩散蒙特卡罗(DMC)方法研究了碳环的结构性质和热力学性质。我们基于DMC的几何优化表明，当n>；=3时，多元C-4N和累积型C-4N(+)(2)环都表现出键长变化，这被认为是由于Jahn-Teller扭曲所致。在最近合成的一种C-18分子中，实验观察到即使是在(4N+2)碳环中也存在键长变化。通过对C-4N和C4N+2的DMC结合能的比较，我们全面地描述了小碳环中Huckel规则和Jahn-Teller扭曲之间的竞争：对于n<；5，前者比后者更稳定，其中C4N+2环比C-4N更稳定，而C-4N环和C4N+2一样稳定，其中Jahn-Teller扭曲引起的二聚化效应更重要。
Structural properties and energetics of carbon rings are studied with the diffusion Monte Carlo (DMC) method. Our DMC-based geometry optimization reveals that both polyynic C-4n and cumulenic C-4n (+) (2) rings exhibit bond length alternations for n >= 3, which is understood to be due to Jahn-Teller distortions. The bond length alternation even in a cumulenic (4n + 2) carbon ring was experimentally observed in a recently synthesized C-18 molecule. From a comparison of the DMC cohesive energies of C-4n with those of C4n + 2, we present a comprehensive picture of the competition between Huckel's rule and Jahn-Teller distortion in small carbon rings; the former is more dominant than the latter for n < 5 where C4n + 2 rings are more stable than C-4n, while C-4n rings are as stable as C4n + 2 for n < 5 where dimerization effects due to Jahn-Teller distortion are more important.