  We theoretically propose Ac$_3$Ni$_2$O$_7$, La$_2$BaNi$_2$O$_6$F, and
La$_2$SrNi$_2$O$_6$F compounds to be benchmark materials for bilayer nickelate
superconductivity. The stable phase of Ac$_3$Ni$_2$O$_7$ and
La$_2$BaNi$_2$O$_6$F are found to be $I4/mmm$ without the lattice distortion
caused by octahedra rotation at ambient pressure, where as the lattice
distortion in La$_2$SrNi$_2$O$_6$F can be suppressed with relatively small
external pressure of 4 GPa. The magnetism, electronic structure and spin
susceptibilities of Ac$_3$Ni$_2$O$_7$ are extremely close to those of
La$_3$Ni$_2$O$_7$ at 30 GPa. The ground state of La$_2$BaNi$_2$O$_6$F and
La$_2$SrNi$_2$O$_6$F are antiferromagnetically coupled checkerboard bilayer
with sizable magnetic moment on Ni. In addition, the inter-layer coupling
$J_{\perp}$ between Ni-bilayers in La$_2$BaNi$_2$O$_6$F or La$_2$SrNi$_2$O$_6$F
is only $\sim$ 1/10 of that in Ac$_3$Ni$_2$O$_7$ or La$_3$Ni$_2$O$_7$ at 30
GPa. We argue that these compounds may serve as superconducting candidates at
ambient pressure and can be employed to testify theoretical proposals for
bilayer nickelate superconductivity.
