We investigate the evolution of electronic structure with dimensionality (d) of Ni-O-Ni connectivity in divalent nickelates, NiO $(3\mathrm{}-d),$ ${\mathrm{La}}_2{\mathrm{NiO}}_4,$ ${\mathrm{Pr}}_2{\mathrm{NiO}}_4$ $(2\mathrm{}-d),$ ${\mathrm{Y}}_2{\mathrm{BaNiO}}_5$ $(1\mathrm{}-d)$ and ${\mathrm{Lu}}_2{\mathrm{BaNiO}}_5$ $(0\mathrm{}-d)$, by analyzing the valence band and the Ni $2p$ core-level photoemission spectra in conjunction with detailed many-body calculations including full multiplet interactions. Experimental results exhibit a reduction in the intensity of correlation-induced satellite features with decreasing dimensionality. The calculations based on the cluster model, but evaluating both Ni $3d$ and O $2p$ related photoemission processes on the same footing, provide a consistent description of both valence-band and core-level spectra in terms of various interaction strengths. While the correlation-induced satellite features in NiO is dominated by poorly screened $d^8$ states as described in the existing literature, we find that the satellite features in the nickelates with lower dimensional Ni-O-Ni connectivity are in fact dominated by the over-screened $d^{10}{\underset{¯}{L}}^2$ states. It is found that the changing electronic structure with the dimensionality is primarily driven by two factors: (i) a suppression of the nonlocal contribution to screening; and (ii) a systematic decrease of the charge-transfer energy $\Delta$ driven by changes in the Madelung potential.

• Received 12 August 1998

DOI:https://doi.org/10.1103/PhysRevB.59.12457