Fig. 4. The charge density difference plots (ranging from –0.01 to 0.01e Å^–3) that contain the X–Ni bond and the corresponding Bader charge (Q/e) in the X/Ni(100) systems: (a) B/Ni(100); (b) C/Ni(100); (c) N/Ni(100); (d) O/Ni(100); (e) S/Ni(100); (f) Se/Ni(100); (g) Te/Ni(100).