MC_(20)F_(20)(M=Li,Na,Be和Mg)几何结构和电子性质的密度泛函计算研究

Density functional study on the geometric and electronic properties of MC_(20)F_(20)(M=Li,Na,Be,Mg)

采用密度泛函理论(density functional theory,DFT)中的广义梯度近似(generalized gradient approximation,GGA)对MC20F20(M=Li,Na,Be和Mg)的几何结构和电子性质进行了计算研究.几何结构研发现:随着内掺原子序数的增加,金属原子M对C20F20中的C—C键的影响越来越大,而对C—F键的影响甚微.掺杂能计算表明:MC20F20的掺杂能均为负值,需要在一定的实验条件下才能被合成.内掺碱金属和碱土金属分别产生了两类截然不同的能隙和磁性.其中,内掺碱金属的能隙非常小,且带有1μB的净磁矩,表现出磁性;而内掺碱土金属的能隙比C60的能隙还大,净自旋为0,表现出非磁性.

The generalized gradient approximation （GGA） based on density functional theory（DFT）is used to analyze the geometric and electronic properties of the endohedral fullerene MC 20 F 20 （M=Li,Na,Be,and Mg）. The analysis of geometric structure indicates that the C—C bond length increases with the atomic number M,while the C—F bond length hardly changes. The doping energy of all kinds of MC 20 F 20 is negative,indicating that the encapsulation would proceed under certain conditions. The electronic structure demonstrates that MC 20 F 20 （M=Li and Na） and MC 20 F 20 （M=Be and Mg） have different energy gaps and magnetic moments. The energy gaps of MC 20 F 20 （M=Li and Na） are very small,while the energy gaps of MC 20 F 20 （M=Be and Mg） are larger than that of C 60. On the other hand,the MC 20 F 20 （M=Li and Na） have 1μB magnetic moment,whereas the magnetic moments of MC 20 F 20 （M=Be and Mg） are zero.