Computational Study of Alkaline Earth Metal Atom on Ge11 and Ge12 Clusters

• Main Authors: Hu, Chao-Jie, 胡朝捷
• Other Authors: Hung, Yu-Ming
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/7q8qnz

碩士 === 中國文化大學 === 化學系應用化學碩士班 === 103 === We have used the B3LYP of density functional theory (DFT) and a simple basis set 6-31G* to optimize the structures of the hybrid clusters formed by adsorptions of alkaline earth metal(AEM) on Ge11 and Ge12 . Generally, Be has the best capability of forming covalent bonds with Ge among Be、Mg、Ca. Geometric relaxations//single point energies were carried out at the B3LYP/6-31G*//B3LYP/6-311++G(3df) level; the same method was applied to transition-state search.Our results showed that Be is commonly hypervalent with MTV > 3, higher than the expected value 2, especially in those endohedrons. Hirshfeld charges(HCs) and molecular orbitals indicated that back-donation from hosts facilitated such hypervalency. In CaGe11 and CaGe12 ,Ca-Ge bonds have small Mayer bond orders(MBO) but metal adsorption energies (Ead) are higher than in MgGe11 and MgGe12 because MBOs underestimate the bond ionicities, which are revealed by the obviously positive HCs of Ca atoms. The binding energies (BE) in MGen are comparable with different M and the same n , meaning the contribution of metal adsorption is not significant to the complete dissociation, but the greater stability of Ge12 than Ge11 . However, Eads in MGen (also different M and same n) imply that Be adsorbs strongly on Gen, then in Ca, and then in Mg. Mg-Ge has less covalency than Be-Ge and less iconicity than Ca-Ge that make Mg the weakest adsorbate.