The structure and superconductivity of La₂PrNi₂O₇ under pressure

Nickel-based superconductors have attracted great attention due to the finding of the Ruddlesden–Popper (R–P) bilayer nickelate La 3 Ni 2 O 7 with superconducting critical temperature ( T c ) of 80 K at pressure above 14 GPa. The recent effort has been devoted to the study of La 2 PrNi 2 O 7 , while the detailed structure remains unclear. In this work, we explore the stability and physical properties of such an interesting system by using Density Functional Theory and the U parameter simulation method implemented in VASP. The results show that the enthalpy of La 2 PrNi 2 O 7 is slightly larger than its parent material-bilayer R-P nickelate La 3 Ni 2 O 7 . The electronic structure analysis indicates that near the Fermi level, the e g orbit of Ni dominates and strongly hybridizes with the 2p orbit of O, thereby forming a significant van Hove singularity that is conducive to superconductivity. The Amam phase to the I 4/ mmm phase occurs, accompanied by an increase in the bandwidth of Ni 3d z 2 and an enhancement of the bonding-antibonding splitting (from about 0.5 eV to 1.5 eV), which leads to an increase in the density of states at the Fermi level. Our findings provide insights into the preparation and superconductivity of Ruddlesden–Popper (R–P) bilayer nickelate.