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Understanding molecular adsorption on surfaces underpins many problems in chemistry and materials science. Accurately and efficiently describing the adsorption has been a challenging task for first-principles methods as the process can involve both short-range chemical bond formations and long-range physical interactions, e.g., van der Waals (vdW) interaction. Density functional theory presents an appealing choice for modeling adsorption reactions, although calculations with many exchange-correlation density functional approximations struggle to accurately describe both chemical and physical molecular adsorptions. Here, we propose an efficient density functional approximation that is accurate for both chemical and physical adsorption by concurrently optimizing its semilocal component andmore » the long-range vdW correction against the prototypical adsorption CO/Pt(111) and Ar₂ binding energy curve. The resulting function opens the door to accurate and efficient modeling of general molecular adsorption.« less

Nanoparticle sintering remains a critical challenge in heterogeneous catalysis. In this work, we present a unified deep potential (DP) model based on the Perdew–Burke–Ernzerhof approximation of density functional theory for Cu nanoparticles on three Al₂O₃ surfaces (γ-Al₂O₃(100), γ-Al₂O₃(110), and α-Al₂O₃(0001)). Using DP-accelerated simulations, we reveal that the nanoparticle size-mobility relationship strongly depends on the supporting surface. The diffusion of nanoparticles on the two γ-Al₂O₃ surfaces is almost independent of the size of the nanoparticle, while the diffusion on α-Al₂O₃(0001) decreases rapidly with increasing size. Interestingly, nanoparticles with fewer than 55 atoms diffuse several times faster on α-Al₂O₃(0001) than on γ-Al₂O₃(100)more » at 800 K while expected to be more sluggish based on their larger binding energy at 0 K. The diffusion on α-Al₂O₃(0001) is facilitated by dynamic metal–support interaction (MSI), where Al atoms move out of the surface plane to optimize contact with the nanoparticle and relax back to the plane as the nanoparticle moves away. In contrast, the MSI on γ-Al₂O₃(100) and on γ-Al₂O₃(110) is dominated by more stable and directional Cu–O bonds, consistent with the limited diffusion observed on these surfaces. Our extended MD simulations provide insight into the sintering processes, showing that the dispersity of the nanoparticles strongly influences the coalescence driven by nanoparticle diffusion. We observed that the coalescence of Cu₁₃ nanoparticles on α-Al₂O₃(0001) can occur in a short time (10 ns) at 800 K even with an initial internanoparticle distance increased to 3 nm, while the coalescence on the two γ-Al₂O₃ surfaces are inhibited significantly by increasing the initial internanoparticle distance. These findings demonstrate that the dynamics of the supporting surface is crucial to understanding the sintering mechanism and offer guidance for designing sinter-resistant catalysts by engineering the support morphology.« less

Adsorption of the molecule CO on metallic surfaces is an important unsolved problem in Kohn-Sham density functional theory (KS-DFT). We present a detailed study of carbon monoxide adsorption on fcc (111) surfaces of 3d, 4d, and 5d metals using nonempirical semilocal density functionals for the exchange-correlation energy: the local-density approximation (LDA), two generalized gradient approximations or GGAs [Perdew-Burke-Ernzerhof (PBE) and PBE for solids (PBEsol)], and a meta-GGA [strongly constrained and appropriately normed (SCAN) functional]. The typical error pattern (as found earlier for free molecules and for free transition-metal surfaces), in which results improve from LDA to PBE or PBEsol tomore » SCAN, due to the satisfaction of more exact constraints, is not found here. Instead, for CO adsorption on transition-metal surfaces, we find that, while SCAN overbinds much less than LDA, it overbinds slightly more than PBE. Moreover, the tested functionals often predict the wrong adsorption site, as first pointed out for LDA and GGA in the CO/Pt (111) puzzle. This abnormal pattern leads us to suspect that the errors of PBE and SCAN for this problem are density-driven self-interaction errors associated with incorrect charge transfer between molecule and metal surface. We point out that, by the variational principle, overbinding by an approximate functional would be reduced if that functional were applied not to its self-consistent density for the adsorbed system but to an exact or more correct density for that system. Finally, we show for CO on Pt(111) that the site preference is corrected and the adsorption energy is improved for the PBE functional by using not the self-consistent PBE density but a PBE+U density. The resulting correction to the PBE total energy is much larger for the adsorbed system than for its desorbed components, showing that the error is in the density of the adsorbed system. Furthermore, this seems to solve the Feibelman 2001 CO/Pt(111) puzzle, in principle if not fully in practice.« less

Monolayers of different mutants of bacteriorhodopsin (bR) with purple membranes are deposited on gold (Au) substrates. Optical measurements and density functional theory-based electronic structure calculations are reported for the first time for the bR chromophore, which is the retinal protonated Schiff base. The dielectric function of the chromophore is extracted using spectroscopic ellipsometry. Designed mutants of bR are used to investigate the bonding with the gold substrate and bR–Au bonding changes can be tracked using the optical properties of the retinal fragment.

Many processes of technological and fundamental importance occur on surfaces. Adsorption is one of these phenomena that has received the most attention. However, it presents a great challenge to conventional density functional theory. By starting with the Lifshitz-Zaremba-Kohn second-order perturbation theory, we develop a long-range van der Waals (vdW) correction for physisorption of graphene on metals. The model importantly includes quadrupole-surface interaction and screening effects. The results show that, when the vdW correction is combined with the Perdew-Burke-Enzerhof functional, it yields adsorption energies in good agreement with the random-phase approximation, significantly improving upon other vdW methods. We also find that,more » compared with the leading-order interaction, the higher-order quadrupole-surface correction accounts for about 25$$\%$$ of the total vdW correction, suggesting the importance of the higher-order term.« less

Significance It is primarily at their surfaces that solids interact with their environments. What is the physics behind the measurable properties of clean metallic surfaces? To answer this question, we calculate surface energies, work functions, and surface interlayer relaxations for aluminum and seven d -electron metals, using a sequence of exchange-correlation density functionals of increasing sophistication. While the simplest one, the local density approximation, works well through error cancellation, the usually more realistic Perdew–Burke–Ernzerhof functional underestimates both surface energies and work functions. The more advanced functionals, including the new strongly constrained and appropriately normed (SCAN) and SCAN+rVV10, demonstrate the unexpectedmore » importance of intermediate and long-range van der Waals attraction (seamlessly included in the random phase approximation).« less

We show that intercalation of cations (Na⁺, Ca2⁺, Ni2⁺, and Co2⁺) into the interlayer region of 1T-MoS2 is an effective strategy to lower the overpotential for the hydrogen evolution reaction (HER). In acidic media the onset potential for 1T-MoS₂ with intercalated ions is lowered by ~60 mV relative to that for pristine 1T-MoS₂ (onset of ~180 mV). Density functional theory (DFT) calculations show a lowering in the Gibbs free energy for H-adsorption (ΔGH) on these intercalated structures relative to intercalant-free 1T-MoS₂. The DFT calculations suggest that Na⁺ intercalation results in a $$ΔG_H$$ close to zero. Consistent with calculation, experiments showmore » that the intercalation of Na⁺ ions into the interlayer region of 1T-MoS₂ results in the lowest overpotential for the HER.« less