  The abstract of Phys. Rev. Lett. 121, 157001 (2018) claims to "demonstrate,
using ab initio computations, a new trend suggesting that the cuprates with
stronger out-of-CuO$_{2}$-plane chemical bonding between the apical anion (O,
Cl) and apical cation (e.g., La, Hg, Bi, Tl) are generally correlated with
higher $T_{c\,\max}$ in experiments". We point out that this trend is included
in the long-known [Phys. Rev. Lett. 87, 047003 (2001)] correlation of
$T_{c\,\max}$ with the hopping range of the electrons at (the most
interlayer-bonding sheet of) the Fermi-surface. Contrary to the impression
given in Phys. Rev. Lett. 121, 157001 (2018), the correlation mentioned in
Phys. Rev. Lett. 87, 047003 (2001) is not simply with the distance, $d_{A},$ of
apical oxygen from the nearest CuO$_{2}$ plane; but rather, as stated in the
abstract of Phys. Rev. Lett. 87, 047003 (2001), "It is controlled by the energy
of the axial orbital, a hybrid between Cu 4$s$, apical-oxygen 2$p_{z},$ and
farther orbitals."
