School of Electronic Science and Engineering, Southeast University, Nanjing, 210096, China.
J Mol Model. 2010 Mar;16(3):469-73. doi: 10.1007/s00894-009-0564-4. Epub 2009 Jul 28.
Based on experimental zinc blende and wurtzite models of CdSe nanocrystals, four clusters of CdSe, seven Se-Cd-ligand structures, and their characters are studied at DFT/B3LYP/Lanl2dz theoretical level. Cd(3)Se(3), (Cd(3)Se(3))(2) and (Cd(3)Se(3))(3) clusters which have a ring with six atoms are similar to wurtzite structures, Cd(4)Se(4) have resemblant conformation with zinc blende for they are all composed of tetrahedron. Calculated Raman spectra of Cd(3)Se(3), Cd(4)Se(4), (Cd(3)Se(3))(2) and (Cd(3)Se(3))(3) are about 175 cm(-1) which is consistent with the experimental result. Then, through investigation of Se-Cd-ligand clusters, we find that all Se-Cd-ligand structures have similar characters because main influence of ligands on nanocrystals comes from thiol. Finally, we testify that both solvent and ligand make absorption peaks shift to blue, compared with those in gas phase and without ligand. Under these conditions, calculated data of four clusters are almost identical with the absorption peaks of CdSe nanocrystals. Besides, we also prove that the absorption peaks of four clusters are the transitions from HOMO to LUMO or from d to p orbitals. And HOMO-LUMO gaps reduce in order of Cd(3)Se(3), (Cd(3)Se(3))(2) and (Cd(3)Se(3))(3), which is induced by the quantum size effect.
基于闪锌矿和纤锌矿结构的 CdSe 纳米晶的实验模型，在 DFT/B3LYP/Lanl2dz 理论水平上研究了四个 CdSe 簇、七个 Se-Cd-配体结构及其性质。具有六个原子环的 Cd(3)Se(3)、(Cd(3)Se(3))(2) 和 (Cd(3)Se(3))(3) 簇类似于纤锌矿结构，而 Cd(4)Se(4)与闪锌矿结构具有相似的构象，因为它们都是由四面体组成的。Cd(3)Se(3)、Cd(4)Se(4)、(Cd(3)Se(3))(2) 和 (Cd(3)Se(3))(3) 的计算拉曼光谱约为 175cm(-1)，与实验结果一致。然后，通过对 Se-Cd-配体簇的研究，我们发现所有的 Se-Cd-配体结构都具有相似的性质，因为配体对纳米晶体的主要影响来自于巯基。最后，我们证明溶剂和配体都会使吸收峰蓝移，与气相和无配体的情况相比。在这些条件下，四个簇的计算数据与 CdSe 纳米晶体的吸收峰几乎一致。此外，我们还证明了四个簇的吸收峰是 HOMO 到 LUMO 或 d 到 p 轨道的跃迁。并且 HOMO-LUMO 能隙按 Cd(3)Se(3)、(Cd(3)Se(3))(2) 和 (Cd(3)Se(3))(3) 的顺序减小，这是由量子尺寸效应引起的。
