The reaction barriers of (He+C60(He＠60)) have been calculated by the quantum-chemical method EHMO/ASED in the following four paths: (1) penetrate through the pentagon on the C60 cage; (2) penetrate through the hexago...The reaction barriers of (He+C60(He＠60)) have been calculated by the quantum-chemical method EHMO/ASED in the following four paths: (1) penetrate through the pentagon on the C60 cage; (2) penetrate through the hexagon on the C60 cage,(3) penetrate through the short bond; (4) penetrate through the long bond. Corresponding to each path, there are two choices: (a) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a planar extension and a concerned window is formed, (b) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a spherical extension and a concerned window is formed. The results are given in Figs. 1-2 and Tables 1-2. It is shown that the reaction through path (4) with choice (a) has the least reaction baxrier, being optimum.At that case, a window of 9-membered ring is formed. Because the window extension of C6H6 is more free than that of C60, the barrier of He penetrating through C6H6 will be lower than that of He penetrating through C60.展开更多
In 1985, Kroto, SmaUey and their co-workers discovered a series of new forms of elementary carbons in experiments: many carbon atoms gather together to form quite stable clusters in gas-phase, among which C<sub>...In 1985, Kroto, SmaUey and their co-workers discovered a series of new forms of elementary carbons in experiments: many carbon atoms gather together to form quite stable clusters in gas-phase, among which C<sub>60</sub> is of the greatest abundance. Since then, many experimental and theoretical scientists have paid more attention to C<sub>60</sub>. They found展开更多
In this paper, we carry out the calculation on the system (X@C60)(X=Li, Na, K, Kb, Cs; F, Cl, Br, I), where the position of X changes along 5 typical symmetry directions. For the calculation of quantum chemistry we us...In this paper, we carry out the calculation on the system (X@C60)(X=Li, Na, K, Kb, Cs; F, Cl, Br, I), where the position of X changes along 5 typical symmetry directions. For the calculation of quantum chemistry we use EHMO/ASED method, for the calculation of molecular mechanics we use Buckingham potential (exp-6-1) function, and for the calculation of thermo-chemical cycle we use individually isolating the processes such as the structure variation, charge transfer and charge distribution, and their interactions etc. The calculation results show that (1) In the region of radius r≈0.2 nm of the Ceo cage, the potential field is nearly spherical; (2) Except for Li and Na, the systems are the most stable with minimum energies at the center of C60 cage. For Li and Na, the systems are the most stable with minimum energies at r≈0.16 nm and r≈0.13 nm, respectively. In view of the interactive region of chemical bonds, the interactions between X and the C60 cage do not belong to the classical chemical bonds; (3) The non-bonding interaction between the X and C60 cage are not purely electro-static, in which the electro-static interactions only occupy -90% at most on an average. The repulsion owing to the overlap of the electron cloud and the attraction owing to the dispersion can not be neglected. These two interactions determine the variations of size and trend of the system energies with r; (4) The polarization due to the position of X deviating from the center of C60 cage plays an important role at the most stable positions of Li and Na.展开更多
文摘The reaction barriers of (He+C60(He＠60)) have been calculated by the quantum-chemical method EHMO/ASED in the following four paths: (1) penetrate through the pentagon on the C60 cage; (2) penetrate through the hexagon on the C60 cage,(3) penetrate through the short bond; (4) penetrate through the long bond. Corresponding to each path, there are two choices: (a) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a planar extension and a concerned window is formed, (b) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a spherical extension and a concerned window is formed. The results are given in Figs. 1-2 and Tables 1-2. It is shown that the reaction through path (4) with choice (a) has the least reaction baxrier, being optimum.At that case, a window of 9-membered ring is formed. Because the window extension of C6H6 is more free than that of C60, the barrier of He penetrating through C6H6 will be lower than that of He penetrating through C60.
基金Project supported by the National Natural Scienoe Foundation of China
文摘In 1985, Kroto, SmaUey and their co-workers discovered a series of new forms of elementary carbons in experiments: many carbon atoms gather together to form quite stable clusters in gas-phase, among which C<sub>60</sub> is of the greatest abundance. Since then, many experimental and theoretical scientists have paid more attention to C<sub>60</sub>. They found
基金Project supported by the National Natural Science Foundation of China.
文摘In this paper, we carry out the calculation on the system (X@C60)(X=Li, Na, K, Kb, Cs; F, Cl, Br, I), where the position of X changes along 5 typical symmetry directions. For the calculation of quantum chemistry we use EHMO/ASED method, for the calculation of molecular mechanics we use Buckingham potential (exp-6-1) function, and for the calculation of thermo-chemical cycle we use individually isolating the processes such as the structure variation, charge transfer and charge distribution, and their interactions etc. The calculation results show that (1) In the region of radius r≈0.2 nm of the Ceo cage, the potential field is nearly spherical; (2) Except for Li and Na, the systems are the most stable with minimum energies at the center of C60 cage. For Li and Na, the systems are the most stable with minimum energies at r≈0.16 nm and r≈0.13 nm, respectively. In view of the interactive region of chemical bonds, the interactions between X and the C60 cage do not belong to the classical chemical bonds; (3) The non-bonding interaction between the X and C60 cage are not purely electro-static, in which the electro-static interactions only occupy -90% at most on an average. The repulsion owing to the overlap of the electron cloud and the attraction owing to the dispersion can not be neglected. These two interactions determine the variations of size and trend of the system energies with r; (4) The polarization due to the position of X deviating from the center of C60 cage plays an important role at the most stable positions of Li and Na.
