应用密度泛函理论研究(MgO)nCu团簇的结构和电子性质

Study on the structure and electronic properties of(MgO)_nCu(n=2～8)clusters applying density functional theory

采用密度泛函理论中的广义梯度近似(GGA)对(MgO)nCu(n=2～8)团簇的几何构型进行优化,并对能量、频率和电子性质进行了计算.结果表明:(MgO)nCu的最低能量结构是在(MgO)n的最低能量结构或者亚稳态结构的基础上吸附一个Cu原子生长而成,且Cu原子的吸附以桥位为主.布局数分析表明Cu原子的吸附对近邻原子的电荷影响比较大,Cu原子得失电子的方向可以改变.Cu原子的吸附增强了(MgO)n的化学活性.二阶能量差分,垂直电离势和分裂能表明(MgO)4Cu是最稳定的团簇.

The geometric structures of(MgO)nCu(n=2～8)clusters are optimized by using the generalized gradient approximation(GGA)density functional theory.Their Energy,vibration frequency and electronic properties are calculated.The results show that the geometries of(MgO)nCu can be obtained by adsorbing a Cu atom on the lowest energy structures or matastable structures of(MgO)n.Bridge-site is energetically preferred among various possible adsorption sites.The Mulliken populations indicate that the adsorbed Cu atom only causes charge redistributions of the atoms near itself and the direction of charge transferring for Cu atom may change.In addition,the energy gaps between the highest occupied and lowest unoccupied molecular orbitals(HOMO-LUMO)remarkably decrease compared with the pure(MgO)n(n=2～8)clusters.Furthermore,the investigations on the second-order difference,vertical ionization potential and fragmentation energies show that(MgO)4Cu cluster has enhanced stabilities.