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The rare-earth nickelates with the exception of LaNiO₃ are found to exhibit a bond disproportionated state. This was shown [1] to emerge in the regime where the effective charge transfer energy between the O p and the Ni d unoccupied states was negative. We perform ab-initio

electronic structure calculations and perturb the bond disproportionated state by various routes. One route adopted is to explore carrier doping by doping at the rare earth site. Both electron and hole doping are found to tune the effective charge transfer energy, with the latter increasing it and providing a route to tune to a positive value, where we do not expect a bond disproportionated state. Our calculations indicate that the doped carriers are localized in the vicinity of the dopant, while the bond disproportionation of the rest of the lattice survives.

[1]. B. Mandal et al., arXiv 1701.06819.