A transferable prediction model of molecular adsorption on metals based on adsorbate and substrate properties.

Surface adsorption is one of the fundamental processes in numerous fields, including catalysis, the environment, energy and medicine. The development of an adsorption model which provides an effective prediction of binding energy in minutes has been a long term goal in surface and interface science. The solution has been elusive as identifying the intrinsic determinants of the adsorption energy for various compositions, structures and environments is non-trivial. We introduce a new and flexible model for predicting adsorption energies to metal substrates. The model is based on easily computed, intrinsic properties of the substrate and adsorbate, which are the same for all the considered systems. It is parameterised using machine learning based on first-principles calculations of probe molecules (e.g., H2O, CO2, O2, N2) adsorbed to a range of pure metal substrates. The model predicts the computed dissociative adsorption energy to metal surfaces with a correlation coefficient of 0.93 and a mean absolute error of 0.77 eV for the large database of molecular adsorption energies provided by Catalysis-Hub.org which have a range of 15 eV. As the model is based on pre-computed quantities it provides near-instantaneous estimates of adsorption energies and it is sufficiently accurate to eliminate around 90% of candidates in screening study of new adsorbates. The model, therefore, significantly enhances current efforts to identify new molecular coatings in many applied research fields.

Corrosion Protection through Naturally Occurring Films: New Insights from Iron Carbonate.

Despite intensive study over many years, the chemistry and physics of the atomic level mechanisms that govern corrosion are not fully understood. In particular, the occurrence and severity of highly localized metal degradation cannot currently be predicted and often cannot be rationalized in failure analysis. We report a first-principles model of the nature of protective iron carbonate films coupled with a detailed chemical and physical characterization of such a film in a carefully controlled environment. The fundamental building blocks of the protective film, siderite (FeCO3) crystallites, are found to be very sensitive to the growth environment. In iron-rich conditions, cylindrical crystallites form that are highly likely to be more susceptible to chemical attack and dissolution than the rhombohedral crystallites formed in iron-poor conditions. This suggests that local degradation of metal surfaces is influenced by structures that form during early growth and provides new avenues for the prevention, detection, and mitigation of carbon steel corrosion.