Abstract

Density functional calculations in periodic boundary conditions (PBCs) were performed to investigate the structural and electronic properties of neutral and charged M@C₆₀ (M = Li, Na, or K). Minimal energy structures for each compounds were obtained. The structural analysis shows that the geometrical shape of the endohedral fullerenes is not perfectly spherical. In the periodic boundary conditions, only K and K⁺ retain their position in the center of fullerene while (Li) and (Na) are shifted from the center by 1.53 and 0.89 Å respectively. Mulliken population analysis indicated that the M-C₆₀ bond may be purely ionic in the case of encapsulated K and Na, and partly ionic in the case of Li. For all compounds, the highest occupied cluster orbitals (HOCOs), the lowest unoccupied cluster orbitals (LUCOs) and the Gap energy were calculated and compared with literature.

The results obtained using PBCs approach show that the simulation model used in this study is indeed appropriate, it not only agrees very well with other theoretical methods but also is consistent with experimental results for C₆₀. Furthermore, this model provide new Gap values for (M@C₆₀) compound (M = Li, Na, or K) that can be used by the scientific community for deriving other electronic properties.

中文翻译：

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周期性边界条件下内面体富勒烯M @ C 60（M = Li，Na或K）的理论研究

摘要

进行周期性边界条件（PBC）的密度泛函计算，以研究中性和带电M @ C ₆₀（M = Li，Na或K）的结构和电子性质。获得了每种化合物的最小能量结构。结构分析表明，内面富勒烯的几何形状不是完美的球形。在周期性边界条件下，只有K和K ⁺保留在富勒烯中心的位置，而（Li）和（Na）分别从中心偏移1.53和0.89Å。Mulliken人口分析表明，MC ₆₀在包封的K和Na的情况下，键可以是纯离子性的，在Li的情况下，键可以是部分离子性的。对于所有化合物，计算出最高的占据簇轨道（HOCO），最低的未占据簇轨道（LUCO）和空位能，并将其与文献进行比较。

使用PBCs方法获得的结果表明，本研究中使用的仿真模型确实是合适的，它不仅与其他理论方法非常吻合，而且与C _60的实验结果一致。此外，该模型为（M @ C ₆₀）化合物（M = Li，Na或K）提供了新的Gap值，科学界可以将其用于推导其他电子特性。