Density Functional Theory Study Of Fullerene-type Cluster Structures

Nowadays,with the rapid increase of computer capabilities and the development of theoretical methods,quantum chemical calculations can be used to handle larger systems and more complex chemical problems.In this dissertation,density functional theory?DFT?calculations were carried out to calculate the?boro?fullerenes such as C₇₆ and B₈₀ trapping different metallic species.The research focuses on their geometric structures,electronic properties,dynamic behavior,and spectral characteristics.First,we proposed that the Th@C₇₆ structure synthesized in recent experiments should be based on the IPR T_d?19151?-C₇₆ cage,and the inner Th atoms formally transfers four electrons to carbon cage.The high binding energy and large HOMO-LUMO energy gap indicate that the molecule has good thermodynamic and kinetic stability.Interestingly,with increased temperature,the metal could hop along a novel octahedron-shape trajectory with the T_d cage symmetry almost intact.This dynamic behavior suggests that it may have potential applications in nanodevice design.Second,we theoretically predicted two new endohedral borofullerenes M₂@B₈₀?M=Sc,Y?.Both of the complexes exhibited large binding energies and sizable HOMO-LUMO gap energies,and exhibited good stability at room temperature and high temperature.In contrast to the closed-shell Y₂@B₈₀,the ground state of Sc₂@B₈₀ bears an unpaired d electron at each metal atom and is thus paramagnetic.Its magnetic moment could be tuned by changing the metal position within the cage,making the structure likely to be used in the design of single-molecule devices.Finally,we predicted four scandium cluster endohedral metalloborofullerenes by theoretical calculations,namely Sc₂C₂@B₈₀,Sc₃C₂@B₈₀,Sc₃CN@B₈₀ and Sc₃C₂CN@B₈₀.We found that the electron-deficient capping boron atoms on B₈₀ are rather flexible:they preferentially move inward to bond with all the trapped C and N atoms,and consequently lead to strong cluster-cage interactions.We examined the bonding patterns of the X@B₈₀molecules by the QTAIM approach,and disclosed the nature of covalent interation between the metal and cages.To further study the stability of each X@B₈₀,MD simulations were carried out at temperature of 300 and 800 K,confirming that they all have relatively high thermal stabilities.