Geometric, electronic properties and the thermodynamics of pure and Al--doped Li clusters

• Published in: arXiv.org 2006-10
• Main Authors: Mal--Soon, Lee, Gowtham, S, He, Haiying, Kah--Chun Lau, Pan, Lin, Kanhere, D G
• Format: Article
• Language: English
• Subjects: Bonding strength; Clusters; Covalent bonds; Diffusion; Dimers; Impurities; Molecular dynamics
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0609215

The first--principles density functional molecular dynamics simulations have been carried out to investigate the geometric, the electronic, and the finite temperature properties of pure Li clusters (Li\(_{10}\), Li\(_{12}\)) and Al--doped Li clusters (Li\(_{10}\)Al, Li\(_{10}\)Al\(_2\)). We find that addition of two Al impurities in Li\(_{10}\) results in a substantial structural change, while the addition of one Al impurity causes a rearrangement of atoms. Introduction of Al--impurities in Li\(_{10}\) establishes a polar bond between Li and nearby Al atom(s), leading to a multicentered bonding, which weakens the Li--Li metallic bonds in the system. These weakened Li--Li bonds lead to a premelting feature to occur at lower temperatures in Al--doped clusters. In Li\(_{10}\)Al\(_2\), Al atoms also form a weak covalent bond, resulting into their dimer like behavior. This causes Al atoms not to `melt' till 800 K, in contrast to the Li atoms which show a complete diffusive behavior above 400 K. Thus, although one Al impurity in Li\(_{10}\) cluster does not change its melting characteristics significantly, two impurities results in `surface melting' of Li atoms whose motions are confined around Al dimer.