  Effective models are constructed for a newly discovered superconductor
(Nd,Sr)NiO2, which has been considered as a possible nickelate analogue of the
cuprates owing to the d9 electron configuration. Estimation of the effective
interaction, which turns out to require a multiorbital model that takes account
of all the orbitals involved on the Fermi surface, shows that the effective
interactions are significantly larger than in the cuprates. A fluctuation
exchange study for the model indicates that dx2-y2-wave superconductivity is
likely to occur as in the cuprates, where the transition temperature in the
nickelate can be lower from the cuprates due to the larger interaction and
narrower bandwidth.
