First-Principles Calculations Of Atom Adsorption On Silicene

Adsorbing foreign atoms on silicene has significant effect on the practical applications. The adsorption of metal atoms provides a route to modify the electronic properties of silicene. Furthermore, the adsorption characteristic of lithium on silicene also provides a guarantee for silicene as an anode of lithium ion battery. However, the adsorption and diffusion of metal atoms on silicene are always affected by various environments, such as strain and hydrogenation. Motivated by this, in this thesis we study the adsorption and diffusion of atoms on the silicene with different environments by using the first-principles plane-wave pseudopotential method. Our work is mainly divided into two parts:(1) Structures and energies of Li-adsorbed silicene under a biaxial strain are studied. According to the optimized structures, the Li-adsorbed silicene basically keep their original configurations without distortion when ensile and certain compressive strain(ε≥-4%) are applied, while the silicene plane bulges towards the Li atom when a larger compressive strain(ε=-4.5% or-5%) is applied. It is found that imaginary frequencies appear in the phonon spectra when the large compressive strains are applied on silicene. The results of phonon spectra indicate that the instability of silicene under the compressive strain results in the significant distortion of silicene after the lithium adsorption.(2) Adsorption and diffusion of alkali metal atoms(Li, Na, K) and alkali earth metal atoms(Be, Mg, Ca) on hydrogenated silicene are studied. And the results of hydrogenated silicene are compared with those of perfect silicene. Our calculations show that for the atoms considered in our work, the adsorption energies on hydrogenated silicene is largely smaller than those on silicene. The diffusion energies of the alkali metal atoms on silicene is insensitive to the status of silicene, namely hydrogenated or perfect. However, the diffusion energies of the alkali earth metal atoms on hydrogenated silicene is also significantly smaller than those on silicene.