Correlation-Driven d-Band Modifications Promote Chemical Bonding at 3d-Ferromagnetic Surfaces

Understanding chemical bonding at molecule-metal interfaces is essential for advancing applications in catalysis, spintronics, and organic electronics. While the Newns-Anderson and d-band models have provided key insights, their applicability remains limited in systems involving large organic adsorbates and correlated metallic substrates. This work investigates the interaction between pentacene (5A) and an oxygen-passivated Fe(100) surface (Fe-O), where oxygen chemisorption gives rise to strong electronic correlations. A combination of photoemission orbital tomography, scanning tunneling spectroscopy, and electronic structure calculations reveals pronounced hybridization between 5A frontier orbitals and the Fe d-states. A tailored DFT+U approach with a negative effective on-site interaction (U_eff = -3.1 eV) captures the experimentally observed reduction in d-band spin splitting and narrowing, consistent with dynamical mean-field theory. These correlation-induced modifications enhance the energetic overlap between metal d-states and molecular orbitals, driving a transition from physisorption to strong chemisorption. Building on these insights, the d-band model is extended to include spatially modulated adsorbate-substrate coupling, successfully reproducing the experimentally observed orbital substructures. These findings offer a tractable route for incorporating many-body effects into simplified chemisorption models, enabling predictive insights into molecule-metal bonding at correlated surfaces and guiding the design of 3d-metal catalysts and organic spintronic interfaces.