  The recent discovery of high-T$_{c}$ superconductivity (HTS) in Sr-doped
NdNiO$_2$ has sparked a renewed interest in investigating nickelates as cuprate
counterparts. Parent cuprates [Cu$^{2+}$: d$^9$] are antiferromagnetic
charge-transfer insulators with the involvement of a single d$_{x^2-y^2}$ band
around the Fermi level and strong $p-d$ hybridization. In contrast,
isoelectronic NdNiO$_2$ [Ni$^+$: d$^9$] is metallic with a d$_{x^2-y^2}$ band
self-doped by Nd-d states. Using first-principles calculations, we study the
effect of Sr-doping in the electronic and magnetic properties of infinite-layer
nickelates as well as the nature of the holes. We find that hole doping tends
to make the material more cuprate-like as it minimizes the self-doping effect,
it enhances the $p-d$ hybridization, and it produces low-spin (S=0,
non-magnetic) Ni$^{2+}$ dopants in analogy with the S=0 Zhang-Rice singlets
that appear in cuprates.
