First-principles calculations of La 3 Ni 2 O 7 using the SCAN meta-GGA functional

Abstract

Abstract

Abstract The recent discovery of high-temperature superconductivity in nickelates under high pressure has garnered widespread attention. Experimental measurements presents the direct observation of a spin-density wave state, indicating the long-range magnetic order evident. However, ascertaining the presence of long-range magnetic order and identifying the magnetic ground state in high-quality single crystal remains a challenge in experiments. Theoretical calculations yield divergent predictions of the ground-state magnetic order, stemming from limitations in exchange-correlation functionals when addressing the strong electron correlations inherent to these systems. Here, we employ the strongly constrained and appropriately normed (SCAN) meta-GGA functional to investigate the magnetic ground state of La 3 Ni 2 O 7 . This approach circumvents the need for empirically tuned Hubbard U parameters required in conventional DFT+U calculations, while also eliminating metastability issue that compromise computational reliability. Our results demonstrate that the A-type antiferromagnetic configuration constitutes the magnetic ground state in the Amam phase, whereas a double spin stripe (DSS) order without spinless configuration emerges as the favored ground state in the Fmmm phase. We further show that the d x 2 -y 2 and d z 2 orbitals, which lie in close proximity to the Fermi level, mediate enhanced superexchange interactions under increasing pressure — a key factor driving the emergence of high-temperature superconductivity. Moreover, interbilayer magnetic couplings substantially modulate the ground-state enthalpy, generate inequivalent Ni sites, and stabilize the experimentally observed bimodal‑moment DSS state. They should therefore be considered an important ingredient for understanding superconductivity in nickelates. Collectively, our work demonstrates the applicability of the parameter‑free SCAN meta‑GGA functional for investigating strongly correlated nickelates with nearly fully occupied d orbitals.