Theoretical Study On Endohedral Fullerenes Of C₆₀

Since the discovery of fullerenes, the encapsulation of certain atoms and molecules into the fullerenes cage structure has been attracted special attentions. Because of fullerene's low yield, the theoretical study turns out to be very important in the research of fullerenes. As the quantum chemistry theory and modern computer technology greatly develops, theoretical chemistry study plays an important role in the fullerenes field.Some people reported that under the accuracy of B3LYP/PM3-RHF the binding energy of Si@C₆₀ is +52.8kcal/mol. During our studies on C@C₆₀, we found that the structure of C@C₆₀ as well as its electronic properties resemble that of the nonmetal-atom-caged fullerenes. In the C@C₆₀'s case, the C atom stays in the center of the C₆₀ cage while the basic state is triplet. In the cage, the C atom keeps in atomic state without electric charge transfering nor covalent bond process. Under the accuracy of B3LYP(6-31G^*), we found the binding energy of C@C₆₀ to be +0.38kcal/mol.By the method of HF and B3LYP density function, we do geometric optimization to compound Ge@C₆₀ where the caged atom Ge is another element of IVA group. With the resource of computation in hand, we choose the 3-21G basic group and 6-31G basic group for C, and choose LanL2DZ basic group for Ge. The computation results show that the structure and electronic property of Ge@C₆₀ resemble that of other nonmetal-atom-caged-fullerenes. In Ge@C₆₀ the Ge atom is in the center of C₆₀ cage and the basic state is triplet. As the result of the Jahn-Teller effect, the carbon cage turns distorted and the whole molecule's symmetry decreases to C_2h. The computation results show that the Ge@C₆₀'s binding energy is 3.28kcal/mol, which indicates the Ge@C₆₀ may be got in condensate phase by synthesize.We optimized CH₂@C₆₀, SiH₂@C₆₀, GeH₂@C₆₀, and after calculation we found that CH₂@C₆₀ is C_2v system which can exist stably, SiH₂@C₆₀, GeH₂@C₆₀ are C_s systems which are also stable. According to the binding energy, the stability order of the three compounds is GeH₂@C₆₀2@C₆₀2@C₆₀, which accords with the order of atomic electronegativity Ge2@C₆₀ still have the binding energy of-14.6908kcal/mol.We do some elementary theoretic studies on P@C₆₀. Computation shows that the energy difference between D_5d isomer and I_h isomer is 0.116kcal/mol. According to the value of energy, the two isomers of P@C₆₀ can completely transform to each other in room temperature, which can be used to explain the properties of P@C₆₀'s ESR spectral diagram.