(230g) Modeling Distribution Tendencies of Noble Metals on Fe(100)

Fe-based catalysts have been shown to be highly selective toward the hydrodeoxygenation of biomass derived oxygenates, but they are prone to oxidative deactivation. Promotion with a noble metal has been shown to improve oxidative resistance, but the resistance is only qualitatively understood. To gain quantitative understanding and precise control over HDO catalyst design, the condition-dependent variations in dispersion, agglomeration, and alloying tendency from one promoter to the next must be quantified at the atomistic scale. Accessing this kind of insight would require a prohibitive number of density functional theory (DFT) calculations due to the enormous configurational space of possible dopant loading and surface-alloy geometries. Moreover, DFT-accessible models are limited to length-scales that are often too small to be experimentally relevant. We circumvent these challenges by constructing an accurate and highly predictive lattice gas cluster expansions (LG CEs) whose effective pair and many-body lateral interactions (clusters) are parametrized via state-of-art prediction-focused fittings to a few hundred simpler DFT simulations using small-to-modest sized bimetallic systems. Having a predictive LG CE allows for studies at experimentally relevant length-scales and inclusion of temperature effects that are otherwise inaccessible to ab initio calculations through statistical mechanical sampling techniques like Monte Carlo simulations. Here, we apply this strategy to HDO-active Fe(100) promoted with four precious metals: Pd, Pt, Rh, and Ru. The resultant LG CEs have remarkable predictive accuracy, with predictive errors below 10 meV/site (Figure 1(a)) over a coverage range of 0 to 2 monolayers (top two layers of Fe(100)). An analysis of the effective repulsive and attractive terms (Figure 1(b)) within the ground state configurations (Figure 1(c)) identified for each noble metal reveals a significant disparity in their dispersion tendency. Currently, we predict that the dispersion of the noble metals decreases in the order of Pt, Pd, Rh and Ru, respectively.