Song Bin, Cao Pei-lin
Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China.
J Chem Phys. 2005 Oct 8;123(14):144312. doi: 10.1063/1.2047527.
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to calculate the lowest-energy geometries and electronic structure of neutral gallium clusters containing up to 26 atoms. Harmonic vibrational frequency analysis is undertaken to assure that the lowest-energy geometries are real local minima. With increasing cluster size, we find that the gallium clusters tend to adopt compact structures. The structures comprise triangular units that connect each other with different dihedral angles. The lowest-energy structure can be obtained by capping an atom on the structure of smaller one. The capping site occurs at a site where interactions with more atoms are available. The binding energy evolves monotonically with size, but Ga(8), Ga(14), and Ga(20) exhibit particularly higher stability. Except Ga(2) and Ga(4), all even-numbered gallium clusters we studied are closed-shell singlet states with a substantial highest occupied and lowest unoccupied molecular orbitals gap. The odd-numbered clusters are open shell with a small gap. The size dependence of cluster's ionization potentials and electron affinities is discussed and compared with available experiment.
采用具有广义梯度近似交换关联势的密度泛函理论，计算了含多达26个原子的中性镓团簇的最低能量几何结构和电子结构。进行了谐波振动频率分析，以确保最低能量几何结构是真正的局部极小值。随着团簇尺寸的增加，我们发现镓团簇倾向于采用紧凑结构。这些结构由以不同二面角相互连接的三角形单元组成。最低能量结构可通过在较小团簇结构上覆盖一个原子得到。覆盖位点出现在与更多原子有相互作用的位置。结合能随尺寸单调变化，但Ga(8)、Ga(14)和Ga(20)表现出特别高的稳定性。除了Ga(2)和Ga(4)，我们研究的所有偶数镓团簇都是闭壳单重态，具有较大的最高占据分子轨道和最低未占据分子轨道能隙。奇数团簇是开壳的，能隙较小。讨论了团簇电离势和电子亲和势的尺寸依赖性，并与现有实验进行了比较。
