Structural materials such as advanced metallic alloys with surface passivation layers are essential components in several emerging energy technologies and infrastructure. For instance, refractory metal alloys are used as components in aerospace probes, heat exchangers and claddings in nuclear, solar technologies, etc. Spontaneously formed surface passivation layers are useful as corrosion-resistant coatings, permeation barriers, etc., due to their excellent electronic and chemical insulation

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... inst external stimuli in ambient atmospheric conditions. However, exposure to harsh reactive environments, such as halide-containing aqueous electrolytes, reactive molecules, and gaseous impurities, impacts the integrity of these materials, eventually causing performance failure. This dissertation investigates material performance and response in such reactive environments by combining multiscale modeling methods with data-driven screening approaches. Advances in this work are focused on two general themes: 1) modeling and simulation for the mechanistic understanding of material properties in reactive conditions and 2) machine learning (ML) guided material design with synergistic properties. In the first half of this thesis, multiscale models are developed to investigate the properties of passive alumina, which is widely used due to its insulating character (bandgap ∼9 eV, poor ionic mobility, and electrochemical stability). First, density functional theory (DFT)-based simulations are used to uncover the atomistic and electronic mechanisms responsible for chloride-induced localized corrosion of metals with Al2O3 passive layers in electrochemical conditions. Results demonstrate the increased likelihood of metal depassivation at defect sites in alumina layers, such as surface terminations of grain boundaries, consistent with experimental observations. Second, our results demonstrate the suitability of alumina polymorphs as hydrogen permeation barriers, which is critical to improve hydrogen retention in solid-state hydride ne [...]