The evolution of the equilibrium geometry, binding energy and electronic structure of Pb.Sn (n = l~19) alloy clusters have been calculated by using first ?principles calculations based on density functional theory (DFT). The stability of Pbn clusters is enhanced by adding single Sn atom to Pb, clusters and the theoretical fragmentation behavior gives a well explanation for previous results. As the total atom number N=14 the occurrence of structural transformation from close packed to the layer is detected. The calculated H0M0-LUMO energy gaps tend to firstly increase then decrease, and reach to the maximal value of 1. 6 eV as JV=6, which presents prominent semiconductor behavior and dependence of the cluster size. As NS>7 the Gap suffers an oscillatory reduction and behaves weak transformation from semiconductor to metallicity.%基于密度泛函理论(DFT),采用广义梯度近似(GGA)计算了PbxSn(n=1～19)合金团簇的结构演化、结合能和电子结构.结果表明Sn原子的掺杂增强了Pbn团簇的稳定性,其碎裂行为也很好地符合了已有的实验结果.随着PbnSn合金团簇尺寸的增加,其几何结构由类似于密堆积构型向松散构型演化,具体的转变尺寸为总原子数N=14.PbnSn团簇的HOMO-LUMO能隙呈现出先增加后降低的趋势,在6原子时达到最大值1.6 eV,表现出显著的半导体性质和尺寸依赖.当N≥7时,能隙振荡减小,呈现出微弱的半导体性向金属性的转变行为.
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