First-principles Study On The Structural And Electronic Properties Of Middle-Small Size (CdS)_n And (CdTe)_n Clusters

In last decades, semiconductor clusters have been one of hot research spots, not only as a result of their impotant roles in basic research, but also as a result of their potentail applications in the microelectronic and photoelectronic domains. Recently, II~VI semiconductor(CdS,CdSe,CdTe and HgTe)clusters and quantum dots, because of their impotent use in tunable light emitted devices (LED) and quantum dot lasers, have attracted a lot of interest.However, there have been much fewer first principles studies for (CdS)n and (CdTe)n clusters up to now. So it is significant to have a further study on the structural and electronic properties of II~VI semiconductor clusters or quantum dots by using first principles. It is helpful for us to fully know the structural and the electronic natures of II~VI semiconductor clusters.In this paper, by using the first-principles method based on density functional theory within generalied gradient approximation(GGA) (DMOL3 code), we calculated the structures of the ground states of middle-small size II~VI semiconductor (CdS)n and (CdTe)n (1≤n≤11) clusters,binding energy and energy gap ect.To compare the results, we also carriedout the calculations within the local density approximation(LDA).We come to the following conclusions:(1) Our results of (CdSe)n (1≤n≤8)are in good agreement with M.C.Troparevsky et al., and the results of (HgTe)n (1≤n≤8) are in good agreement with calculatied by CASTEP code. All these show that our calculation scheme is reasonable.(2) The binding energy of (CdS)n (1≤n≤11)is bigger when the sizes is larger. 1≤n≤8, The tendencies of (CdS)n both the binding energies and energy gaps varing with the size are the almost the same with those of M.C.Troparevsky et al.'s. It shows that our calculation results are reasonable. The (CdS)n (1≤n≤11)clusters with 6 and 12 atoms have substantially higher HOMO-LUMO gaps, with 10 and 16 atoms have substantially lower HOMO-LUMO gaps, and they also exhibit local maxima and local minimum in the binding energies.(3) The (CdTe)n (1≤n≤11)clusters with 6 and 12 atoms exhibit local maxima in the binding energies, but with 8 and 12 atoms have substantially higher HOMO-LUMO gaps. The results about (CdTe)n clusters have not been reported before. The binding energy, energy gap vs. size of (CdTe)n clusters have difference with...