x Si structures were also studied by DFT calculations following the procedure proposed by Chevrier and Dahn. We used a repeated cell scheme with 12 silicon atoms and N lithium atoms per unit cell, with N ∈ [0, 45] covering the hole range of x ∈ [0, 3.75]. Each Li N +1 Si 12 structure was obtained by adding a lithium atom in the greatest void of the Li N Si 12 cell and performing a geometrical optimization of all atomic positions and cell volume. In this case, the calculations were performed with the QUAN-TUM ESPRESSO software, using the PBE xc-functional with a kinetic energy cutoff of 1090 eV and the Brillouin zone integration was done with Monkhorst-Pack grids with a density of 7 k points per Å -1 . The atomic positions and cell volume were optimized employing the BFGS algorithm until the force was less than 0.08 eV/Å for each structure.