密度泛函理论对Ga_mAs_n团簇的结构及稳定性的研究

Structures and stability of small Ga_mAs_n clusters

利用密度泛函理论（DFT）对GamAsn（m=1,2;n=1-5）团簇的几何结构及稳定性进行了研究.在B3LYP/6-31G^＊水平上进行了结构优化和频率分析,得到了GamAsn（m=1,2;n=1-5）团簇的基态和亚稳态结构.结果表明,在GamAsn（m=1,2;n=1-5）团簇中,团簇的稳定性随着总原子数的增多而增大;总原子数相同的团簇,As原子多的团簇比Ga原子多的团簇稳定;最高占据轨道（HOMO）和最低空轨道（LUMO）的能级差（Egap）随As原子数的增加而变化,且大体呈现奇偶交替变化规律;原子间的振动频率均在太赫兹频段,为GaAs团簇纳米材料的太赫兹电磁波检测和太赫兹电磁波辐射提供了依据.

Geometric structures and stability of GamAsn （m = 1,2;n = 1- 5） dusters have been studied using the density functional theory （DFT）. Structural optimization and frequency analysis were carried out at the B3LYP/6-31G^＊ level. All ground state structures and meta-stable state structures of GamAsn （ m = 1,2; n = 1 5） clusters have been obtained. Our calculations reveal the stability of GamAsn （ m = 1,2 ; n = 1 - 5） clusters tends to increase with the increase of the number of total atoms. As-rich clusters are more stable than Ga-rich clusters generally among clusters with the same total atoms. The energy gap Egap between the highest-occupied molecular orbital （HOMO） and the lowest-unoccupied molecular orbital （LUMO） ,which depend on composition of the clusters and show an even/odd alteration with the number of As atoms in the cluster. All vibrating frequencies Gam Asn （m = 1,2;n = 1 - 5） clusters are frequencies of the terahertz wave band, this result will provide the further ideas for detection and radiation of terahertz wave for this material.