  The status of nickelate superconductors in relation to cuprate high
temperature superconductors is one of the concepts being discussed in high
temperature superconductivity in correlated transition metal oxides. New
additions to the class of infinite layer nickelates can provide essential input
relating to connections or distinctions. A recently synthesized compound
\bnoas, which contains isolated `infinite layer' NiO$_2$ planes, may lead to
new insights. Our investigations have discovered that, at density functional
theory mean field level, the ground state consists of an unusual $e_g$ singlet
on the Ni$^{2+}$ ion arising from large but separate Mott insulating gaps in
both $e_g$ orbitals, but with different, anti-Hund's, spin directions of their
moments. This textured singlet incorporates at the least new physics, and
potentially a new platform for nickelate superconductivity, which might be of
an unconventional form for transition metal oxides due to the unconventional
undoped state. We include in this paper a comparison of electronic structure
parameters of Ba$_2$NiO$_2$(AgSe)$_2$ with a better characterized infinite
layer nickelate LaNiO$_2$. We provide more analysis of the $d^8$ anti-Hund's
singlet that emerges in this compound, and consider a minimally correlated
wavefunction for this singlet in an itinerant background, and begin discussion
of excitations -- real or virtual -- that may figure into new electronic
phases.
