The Study On The Structures And Properties Of Alkali Metal-doped Silicon Clusters

Alkali-silicon clusters have attracted a lot of attentions,because it has been known that they serve as promoters in catalysts and can be used as power source material for spaceflight aero-crafts, emitters, and many others. In this paperthesis, the geometry structures, electron affinities and dissociation energy for SinM (n=2-8; M=Na, K) and SinNa2(n=2-7) species have been studied by mean of G3 ab initio techniques. The neutral ground state structure of SinM(n=2-8;M=Na, K) species are described as'attaching structures'in which the M atom is bound to Sin clusters, the ground state structure of anion are described as'substitutional structures'which is derived from Sin+1 by replacing a Si atom with a M atom. For the SinNa2(n=2-7) specie, the distance of two sodium atoms in the netrul ground state structure is farer, and there are Na-Na bond forming in all the ground state structure of anions. The predicted electron affinities for SinNa(n=2-8) is 1.74, 1.88, 1.65, 2.40, 2.01, 1.95 and 2.88eV respectively,and the predicted electron affinities for SinK (n=2-8) is 1.51, 1.45, 1.36, 2.19, 1.76, 1.63 and 2.81eV respectively,the predicted electron affinities for SinNa2(n=2-7) is 0.67, 0.22, 1.17, 1.13, 0.97 and 1.31eV respectively. The dissociation energies of Na or K atom from the lowest energy structure of SinM (n=2-8; M= Na, K) and SinNa2(n=2-7) clusters to exmine relative stabilities. The caculationed results indicate that: for the neutral and ation ground state structures of SinM(n=2-8;M=Na, K) specie, relative stabilities of Si4M and Si7M clusters are worse, Si2M, Si5M and Si8M clusters are more stable; for SinNa2(n=2-7) specie, relative stabilities of Si4Na2 and Si7Na2 neutral clusters are worse, Si3Na2 and Si5Na2 neutral clusters are more stable, relative stabilities of Si3Na2?, Si6Na2? and Si7Na2? anion clusters are worse, and Si2Na2? and Si4Na2? are more stable.