Ab initio investigation of the surface properties of Cu(111) and Li diffusion in Cu thin film

Ab initio density-functional calculations have been performed to investigate the surface properties of Cu(111) and lithium diffusion in copper thin film. The calculation results including lattice constant, cohesive energy, work function and surface energy are in fair agreement with that derived from corresponding experiments. The various diffusion pathways such as diffusion of lithium as a substitution atom and various mechanisms are investigated with ab initio molecular dynamics. The energy barrier has been calculated corresponding to each possible pathway. Theoretically, we have identified that lithium can diffuse through copper thin film by successive nearest neighbor vacancy-atom exchanges, therefore, the nearest neighbor vacancy assisted jumping is deduced to be the most probable by comparing the different mechanisms. It is found that more free diffusion may be observed by increasing the number of copper vacancies in the thin film. It is also confirmed that the diffusion is more obvious as temperature is increased.