NiMgn(n=1—12)团簇的第一性原理研究

采用基于密度泛函理论(DFT)中的广义梯度近似 (GGA),在考虑自旋多重度的情况下，对NiMg_n(n=1—12)团簇进行了构型优化，频率分析和电子性质计算.结果表明：n=1,2时，体系的基态为自旋三重态，n≥3时，为单重态；Ni原子掺杂使主团簇结构发生了明显变化. n≤8时，三角双锥，四角双锥结构主导着NiMg_n基态团簇的生长行为; n在9—12之间时，主团簇Mg_n+1(n=1—12)的基于三棱柱构型的基态演化行为发生了一定程度的改变；n≥6时，Ni原子陷入了主团簇内部；掺杂使体系的平均结合能增大，能隙减小；n=4,6,10是团簇的幻数；不同尺寸团簇的s, p, d轨道杂化中，Ni原子3d, 4p成分所起作用不同； NiMg₆基态结构具有很高的对称性(O_h),很好的稳定性和化学活性，能隙仅为0.25eV. 关键词： n团簇')" href="#">NiMg_n团簇 几何结构 稳定性 化学活性

First-principles study of the NiMgn (n=1—12) clusters

The geometrical structure, frequency and electronic properties of the NiMg_n(n=1—12) clusters have been studied with the generalized gradient approximation (GGA) based on the density functional theory (DFT) with the consideration of spin multiplicity. The results indicate that: when n is 1 or 2, the spin multiplicity of the ground state structures of the clusters is triplet while it is singlet from n≥3. The ground state structures of the host clusters are changed obviously due to the encapsulation of Ni atom for n≤8, the growth patterns of the ground state structures of the NiMg_n clusters are dominated by the trigonal bipyramidal, as well as the octahedron structures. The evolution behaviors of the ground state structures based on the trigonal prism of the host clusters are partly modified from n≥9. The Ni atom completely falls into the center of the host clusters as n≥6. The doping of Ni atoms increases the average binding energy, but reduces the energy gap of the host clusters. n=4, 6 and 10 are the magic numbers. The 3d and 4p orbitals of the Ni atom for different sized clusters play distinct roles in the s-p-d orbital hybridization. The NiMg₆ cluster with higher symmetry O_h not only possesses improved stability, but also has the smallest energy gap (just about 0.25eV) of all of the NiMg_n clusters.