  We investigate the electronic structure of nickelate superconductor NdNiO2
upon hole doping, by means of density-functional theory and dynamical
mean-field theory. We demonstrate the strong intrinsic hybridization between
strongly correlated states formed by Ni-3dx2-y2 orbital and itinerant electrons
due to Nd-5d and Ni-3dz2 orbitals, producing a valence-fluctuating correlated
metal as the normal state of hole-doped NdNiO2. The Hund's rule appears to play
a dominating role on multi-orbital physics in the lightly doped compound, while
its effect is gradually reduced by increasing the doping level. Crucially, the
hole-doping leads to intricate effects on Ni-3d orbitals, such as a
non-monotonic change of electron occupation in lightly doped level, and a
flipping orbital configuration in the overdoped regime. Additionaly, we also
map out the topology of Fermi surface at different doping levels. These
findings render a preferred window to peek into electron pairing and
superconductivity.
