Development of a Transferable Density FunctionalTight Binding Model for Organic Molecules at the Water/Platinum Interface

A computationally efficient and transferable approach for modeling reactions at metal/water interfaces could significantly accelerate our understanding and ultimately development of new catalytic transformations, particularly in the context of the emerging field of biomass conversion. Here, we present a parametrization of Pt-X (X = H, O, C) density functional tight-binding (DFTB) for addressing this need. We firstly constructed Pt-H, Pt-O, and Pt-C repulsive potential splines. These pair-wise parameters were then augmented to include many-body interactions using the Chebyshev Interaction Model for Efficient Simulation (ChIMES). We compare the geometrical and energetic performances of both DFTB and DFTB/ChIMES methods to DFT reference data across a variety of organic molecules at platinum surface from nanoparticles to single-crystal surfaces. DFTB shows limited transferability between extended crystal surfaces to small nanoparticles. This transferability is significantly improved through the introduction of three-body interactions with Pt in DFTB/ChIMES, which provides consistent results across the various systems, with reductions in the RMSD from around 30 kcal/mol in DFTB to around 10 kcal/mol. We demonstrate the stability and reliability of the obtained parameters by performing metadynamics simulations for the adsorption of phenol on Pt(111). We observe that DFTB itself is undersolvating the surface, leading to only one or two chemisorbed water molecule in a c(4x6) unit cell. In contrast, DFTB/ChIMES leads to a coverage of about 0.5 ML and successfully captures the chemisorbed mode of phenol both at the solid/liquid and the solid/gas interface. Furthermore, in agreement with experimental measurements, the adsorption energy at the solid/liquid interface is significantly smaller compared to the solid/gas interface. Furthermore, we highlight that even with DFTB, where we can accumulate dynamics for more than 1 ns for a given system, the simulations are not fully converged.