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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >What Are the Ground State Structures of C-20 and C-24? An Explicitly Correlated Ab Initio Approach
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What Are the Ground State Structures of C-20 and C-24? An Explicitly Correlated Ab Initio Approach

机译：C-20和C-24的基态结构是什么？明确相关的从头算方法

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摘要

A new benchmark study has been performed for six isomers of C-20 and four isomers of C-24 using explicitly correlated methods, together with coupled cluster theory with large basis sets and DFT with advanced functionals. The relative energy trends obtained are extremely sensitive to the methods used. Combining our best CCSD(T)-MP2 difference with our best MP2 basis set limit, the dehydrocorannulene bowl is found to be the most stable for C-20, followed by the cage at about 8 kcal/mol, and the ring at about 46 kcal/mol. For C-24, the D3d cage is found to be the most stable isomer, followed at only a few kilocalories per mole by dehydrocoronene, and at larger separations by then octahedral cage and the ring, respectively. This makes C-24 the smallest classical fullerene. The estimated residual basis set error of the estimated CCSD(T) basis set limit is conservatively expected to be +/-1 kcal/mol. In general, DFT exhibits large errors for relative energies with RMSD values in the 8-34 kcal/mol range. However, among the DFT functionals, the DSD-PBEP86-D3BJ double hybrid comes close to our best ab initio results, while the omega B97X-V range-separated hybrid is in semiquantitative agreement.
机译：使用显着相关的方法，结合具有大基础集的耦合聚类理论和具有先进功能的DFT，对C-20的六个异构体和C-24的四个异构体进行了新的基准研究。获得的相对能量趋势对所使用的方法极为敏感。将我们最好的CCSD（T）-MP2差异与我们最好的MP2基础设置限制相结合，发现脱氢氢化蒽环碗对于C-20最稳定，其次是笼子，保持约8 kcal / mol，环的保持约46大卡/摩尔对于C-24，发现D3d笼是最稳定的异构体，随后每摩尔只有几千卡的脱氢古龙烯，然后是更大的间隔，然后是八面体的笼和环。这使C-24成为最小的经典富勒烯。保守地估计CCSD（T）估计基准限值的估计残基估计误差为+/- 1 kcal / mol。通常，DFT在RMSD值在8-34 kcal / mol范围内时，相对能量表现出较大的误差。但是，在DFT功能中，DSD-PBEP86-D3BJ双重杂交接近我们最好的从头开始的结果，而欧米茄B97X-V范围分离的杂交是半定量的。

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