Extended Data Fig. 4: O-p orbital resolved band structure and EELS spectra from DFT + U calculations.

a-b, DFT + U calculated band structure for La₃Ni₂O₇, including the contributions from different O-p orbitals, for U = 0 (a) and U = 3.5 eV (b) respectively. Different colors represent the contributions from inequivalent oxygen sites within each unit cell. c, Calculated O-p projected DOS for different O sites and different values of U. The inclusion of U shifts the filled bands further below the Fermi energy (highlighted with black dashed arrows), while leaving the empty bands nearly unchanged. d, Calculated O-K edge absorption spectra for different O sites and different values of U, which is Gaussian blurred according to the experimental energy resolution ΔE = 0.6 eV. The spectra are insensitive to U, since the empty bands above Fermi energy is barely modified. For the inner apical O, the prepeak originates mostly from O-p_z states in the upper antibonding γ_a band. For the outer apical O, while the low-energy unoccupied states are also dominated by the p_z orbital, its weight is much smaller than the inner apical one. For the planar O, the prepeak is governed by the O-p_x,y states from the α and β bands mainly of d_x2-y2 character.