Chemical Bonding, Thermodynamic Stability and Thermoelectric Transport in Rare‐Earth Layered Trilayer Nickelate Pm ₄ Ni ₃ O ₈ : A First‐Principles Study

We present a first principles investigation of the structural stability, correlated electronic structure, magnetism, thermodynamic behavior and thermoelectric transport of the layered trilayer nickelate Pm 4 Ni 3 O 8 . Calculations performed within GGA‐PBE, mBJ, DFT+U and DFT+SOC frameworks show that strong on‐site Coulomb interactions in Ni‐3d and Pm‐4f states are essential for describing the correlated metallic ground state. Total energy analysis confirms a ferromagnetic configuration energetically favored over antiferromagnetic ordering, indicating itinerant exchange mediated by Ni‐3d and O‐2p hybridization. Electronic states near the Fermi level are dominated by dispersive and O‐2p bands, while Pm‐4f states remain localized and are mainly influenced by spin orbit coupling. Thermodynamic properties obtained from the quasi‐harmonic Debye model demonstrate lattice stability through normal heat capacity and entropy evolution. Thermoelectric transport coefficients were evaluated using semiclassical Boltzmann theory as a function of chemical potential, enabling analysis of carrier type transitions, multiband compensation, and metallic transport behavior. The small Seebeck coefficient at μ = 0 confirms intrinsic metallic character, while chemical potential shifts enhance thermopower and power factor. These results clarify how 3d–4f correlations, itinerant magnetism and lattice stability govern charge and heat transport in Pm 4 Ni 3 O 8 .