幻数尺寸Li-n-1,Lin,Li+ n+1(n=20,40)团簇的几何结构、电子与光学性质的第一性原理研究

基于密度泛函理论,采用第一性原理分子动力学模拟退火方法,对Li^-_n-1,Li_n,Li⁺_n+1 (n=20,40)的最低能量结构进行了全局搜索. 发现锂团簇的生长模式是以单个或多个嵌套的正多面体为核心,其余原子以五角锥为基本单元围绕核心生长. 基于最低能量结构的第一性原理电子结构计算得到锂团簇的分子轨道能级分布与无结构凝胶模型给出的电子壳层完全一致. 在总电 关键词： 团簇 电子结构 极化率 光吸收

Structural, electronic, and optical properties of Lin-n-1,Lin and Li+n+1(n=20,40)clusters by first-principles calculations

The lowest-energy structures of Li^-_n-1, Li_n and Li⁺_n+1 clusters (n=20, 40) were determined from first-principles simulated annealing followed by geometry optimization within the density functional theory. The growth mechanism of Li_n clusters is based on nested multiple polyhedron. Other atoms form pentagonal pyramid centered on the core polyhedron. From our first-principles calculations, the molecular orbital levels can be divided into several groups, which are in good agreement with the electron shells described by structureless jellium model. With the same amount of valence electrons, the number of ions and charge states in the Li clusters have only little effect on the electronic structures. Li^-₁₉, Li₂₀, Li⁺₂₁ and Li^-₃₉, Li₄₀, Li⁺₄₁ exhibit similar energy level distributions, respectively, indicating that the momentum order is the dominating factor for these clusters. The optical absorption spectra of Li^-_n-1, Li_n and Li⁺_n+1 (n=20, 40) clusters from time-dependent density functional theory calculations show giant resonance phenomenon and the simulated resonance peaks agree with experimental values. With same amount of valence electrons, the polarizability decreases with the number of ions and the optical resonance peaks blueshift as the ionic number increases.