Pt_nAl(n=1—8)小团簇的密度泛函理论研究

采用密度泛函理论方法,在BPW91/LANL2DZ水平下详细研究了Pt n Al(n=1—8)团簇的几何结构、稳定性和电子性质.同时,分析了团簇的结构演化规律、平均结合能、二阶能量差分、能隙、磁性、Mulliken电荷和电极化率.结果表明:除Pt2Al外,所有Pt n Al(n=1—8)团簇的基态几何结构都可以用Al原子替换Pt n+1基态构型中的Pt原子得到,且Al原子位于较高的配位点上.二阶能量差分、能隙的分析结果表明,PtAl和Pt4Al团簇相对其他团簇具有较高的稳定性.Mulliken电荷分析表明,Al原子所带的电荷转移到Pt原子上,Al原子是电荷的捐赠者.磁性的分析说明,单个Al原子的加入对Pt n团簇的平均每原子磁矩随尺寸的变化趋势没有影响,但总体上降低了Pt n团簇的平均磁矩.极化率的研究表明,富Pt团簇的非线形光学效应强,容易被外场极化.

A density functional theory study of small bimetallic PtnAl (n=1–8) clusters

The geometries, stabilities and electronic properties of Pt_nAl (n=1–8) clusters are calculated using density functional theory at BPW91/LANL2DZ level. The stabilities of the ground states of Pt_nAl (n=1–8) clusters are discussed by means of the binding energy, the second difference in energy and energy gaps, and the magnetic properties. Mulliken charges are studied. The growth patterns for different sized Pt_nAl (n=1–8) clusters are of Al-substituted Pt_n+1 clusters and they keep a similar framework of the most stable Pt_n+1 clusters except Pt₂Al. Al atoms in the ground state Pt_nAl isomer tend to occupy the most highly coordinated positions. The analyses of stabilities show that PtAl and Pt₄Al are more stable than other clusters. Mulliken population analysis shows that charges are transferred from Al atoms to Pt atoms, which indicates that Al atom acts as electron donor in all Pt_nAl clusters. The analysis of magnetic property shows that doping an Al atom reduces the average atomic magnetic moment of the host Pd cluster. Pt-rich clusters which have a strong nonlinear optical effect and are easy to polarize by external electromagnetic field.