Fig. 2. X-ray scattering measurements of oxygen-deficient perovskite, NdNiO_2+x, samples B and C.

a, H scans, at constant L, at the Ni L₃ and Nd M₅ edges for sample C are presented without background subtraction. Data for sample D, after removal of a cubic fluorescent background and rescaling for visibility, are included for reference. b, Rocking curves through q = (1/3, 0) on lightly reduced sample B, presented without background subtraction but vertically offset for clarity. c, Illustration of a potential intermediate-phase structure for Nd₃Ni₃O₇ from a top-down view of the a–b plane of NiO₂ where two-thirds of the rows of apical oxygen atoms are removed, forming a 3a₀ supercell along the a axis.

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