Fig. 5

DFT calculation and stability mechanism. a Crystal structures of the c-CoSe₂ (left) and o-CoSe₂ (right). b Schematic structure model of m-CoSe₂ showing the [c-CoSe₂ (100)||o-CoSe₂ (101)] interface. Insets are the atomic models of the o-CoSe₂ (101) and c-CoSe₂ (100) surfaces, respectively. c, d XANES spectra recorded at the Co K-edge (c) and Se K-edge (d) of the Co foil, Se foil, c-CoSe₂, and m-CoSe₂, respectively. Inset in c shows the zoomed view of the Co K-edge spectra. e, f Schematic rigid band diagrams of the c-CoSe₂ (e) and m-CoSe₂ (f). g Calculated free energy of the c-, o-, and m-CoSe₂ unit cells. Insets show corresponding unit cell structures. h DOS of the c-CoSe₂ and m-CoSe₂ with the Fermi level aligned at 0 eV.