Motivated by the recent observation of superconductivity with T_c ~ 80 K in pressurized La₃Ni₂O₇¹, we explore the structural and electronic properties of A₃Ni₂O₇ bilayer nickelates (A = La-Lu, Y, Sc) as a function of pressure (0–150 GPa) from first principles including a Coulomb repulsion term. At ~ 20 GPa, we observe an orthorhombic-to-tetragonal transition in La₃Ni₂O₇ at variance with x-ray diffraction data, which points to so-far unresolved complexities at the onset of superconductivity, e.g., charge doping by variations in the oxygen stoichiometry. We compile a structural phase diagram that establishes chemical and external pressure as distinct and counteracting control parameters. We find unexpected correlations between T_c and the in-plane Ni-O-Ni bond angles for La₃Ni₂O₇. Moreover, two structural phases with significant c⁺ octahedral rotations and in-plane bond disproportionations are uncovered for A = Nd-Lu, Y, Sc that exhibit a pressure-driven electronic reconstruction in the Ni e_g manifold. By disentangling the involvement of basal versus apical oxygen states at the Fermi surface, we identify Tb₃Ni₂O₇ as an interesting candidate for superconductivity at ambient pressure. These results suggest a profound tunability of the structural and electronic phases in this novel materials class and are key for a fundamental understanding of the superconductivity mechanism.

受最近在加压 La ₃ Ni ₂ O ₇ ^{1中观察到}T _c  ~ 80 K超导性的启发，我们探索了A ₃ Ni ₂ O ₇双层镍酸盐（A  = La-Lu, Y, Sc）的结构和电子性质根据第一原理（包括库仑斥力项）作为压力 (0–150 GPa) 的函数。在约 20 GPa 的压力下，我们观察到 La ₃ Ni ₂ O ₇中存在与 X 射线衍射数据不同的斜方晶系到四方晶系的转变，这表明超导性开始时迄今为止尚未解决的复杂性，例如，电荷掺杂的变化在氧化学计量中。我们编制了结构相图，将化学压力和外部压力确立为独特且相互抵消的控制参数。我们发现La ₃ Ni ₂ O _7的T _c和面内Ni-O-Ni 键角之间存在意想不到的相关性。此外，对于A = Nd-Lu、Y、Sc，发现了具有显着c ⁺八面体旋转和面内键歧化的两个结构相，它们在 Ni e _g流形 中表现出压力驱动的电子重建。通过解开费米表面基础氧态与顶端氧态的关系，我们将 Tb ₃ Ni ₂ O ₇确定为环境压力下超导性的一个有趣的候选者。这些结果表明这种新型材料中的结构相和电子相具有深刻的可调性，并且是基本理解超导机制的关键。