Surface Spin Effect in Chemisorption and Catalysis: Computational Robustness

In this work, we show that the spin effect in chemisorption and catalysis is independent of the chosen exchange-correlation functional. Density functional theory simulations were performed to calculate the adsorption energies of carbon monoxide, hydrogen, and oxygen on a cobalt cluster and a cobalt surface. Eight commonly used exchange-correlation functionals were evaluated: three generalized gradient approximation (GGA) functionals (BEEF-vdW, PBE and RPBE), two meta-GGA functionals (RTPSS and r²SCAN), and three hybrid functionals (PBE0, HSE03, HSE06). All functionals were applied to the cluster model, while six were used for the surface. Across all levels of theory, non-spin-polarized ground states exhibit stronger binding than spin-polarized solutions. The adsorption energy difference scales with the local average spin moment, with smaller energy differences corresponding to lower spin moments, providing direct evidence that adsorption energies decrease as the spin moment decreases. The consistency of this trend across all tested functionals highlights the generality and robustness of the spin effect in chemisorption and its impact on catalysis.