Fig. 4.

Computational modeling. a Energy barriers along the Cu⁺ diffusion paths in wurtzite CdSe structure, as calculated using the NEB method (see also Supplementary Figure 6c). The radial diffusion is dominated by successive AB steps, while the axial diffusion is facilitated by alternating AB and AB2 steps. b, c Scheme of the CdSe–Cu₂Se interface (illustrated with a dashed line) with antifluorite Cu₂Se above and zinc blende CdSe below. The structures with defects were obtained by structural optimization and then brought together to illustrate the stacking