Theoretical Study of Endohedral Fullerenes M@C 60 (M = Li, Na, or K) in Periodic Boundary Conditions

Density functional calculations in periodic boundary conditions (PBCs) were performed to investigate the structural and electronic properties of neutral and charged M@C 60 (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-C 60 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 C 60 . Furthermore, this model provide new Gap values for (M@C 60 ) compound (M = Li, Na, or K) that can be used by the scientific community for deriving other electronic properties.