The energetics and dynamics of Li atoms in bulk Si were studied at different Li concentrations on the basis of first principles calculations. It was found that Li prefers to occupy an interstitial site as a shallow donor rather than a substitutional site. The most stable position was the tetrahedral (Td) site. The diffusion of a Li atom in the Si lattice was through a Td–Hex–Td trajectory, where the Hex site was the hexagonal transition site with an energy barrier of 0.58eV. A systematic study was also made of the local structural transition of a LixSi alloy, where x varied from 0 to 0.25. At low dopant concentrations (x = 0 to 0.125), the Li atoms preferred to be separate from each other; resulting in an homogeneous dopant distribution. Starting from x = 0.125, the Li atoms tended to form clusters induced . by lattice distortion, with frequent breaking and re-forming of Si-Si bonds. When x ≥ 0.1875, the Li atoms permanently broke some of the Si-Si bonds; resulting in dangling bonds. These dangling bonds created negatively charged zones, which was the main driving force for Li-atom clustering at high dopant concentrations.

First Principles Study of Lithium Insertion in Bulk Silicon. W.Wan, Q.Zhang, Y.Cui, E.Wang: Journal of Physics - Condensed Matter, 2010, 22[41], 415501