Pb_nSn(n=1～19)合金团簇的结构稳定性及其半导体—金属性转变

Structural stability and semiconductor-metal transition in Pb_nSn(n=1～19) alloy clusters

基于密度泛函理论(DFT),采用广义梯度近似(GGA)计算了Pb_nSn(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Pb_n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Pb_nSn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.Pb_nSn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.

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 Pb. clusters is enhanced by adding single Sn atom to Pb. clus- ters 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 detec- ted. The calculated HOMO-LUMO energy gaps tend to firstly increase then decrease, and reach to the maximal value of 1.6 eV as N=6, which presents prominent semiconductor behavior and dependence of the cluster size. As N≥7 the Gap suffers an oscillatory reduction and behaves weak transformation from semiconductor to metallicity.