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Current fundamental understanding of the reaction mechanisms controlling Cu oxidation encompasses early-stage chemisorption and O surface diffusion, as well as later-stage Cu oxide nano-island nucleation and growth. This understanding cannot broadly predict preferential Cu oxide formation on competing surface defects. Improving understanding on how to control preferential oxide formation can lead to more effective corrosion mitigation and Cu/Cu2O catalyst optimization strategies. Computational methods, such as density functional theory and reactive force field molecular mechanics, linked by a multiscale approach can calculate early-stage O adsorption and diffusion energetics on simulated structures comparable to experimental surface defects. Experimental methods, like environmental transmission electron microscopy, can characterize later-stage preferential Cu oxide formation on competing surface defects. This study aspires to illustrate consistency between early- and later-stage oxidation properties, finding whether computationally modeled differences in O diffusion energetics can be used to explain experimentally observable oxide formation preferences along Cu(011) stepped defects. Upon determining which energetics can be applied to reconcile experimental and computational results, edge-to-edge O diffusion mechanisms are found to contribute to oxide island formation over edge-to-terrace mechanisms. Further analysis determines which arrangements of stepped defects can lead to selective oxidation on competing adjacent stepped defects, reviewing the corners formed by these defects to characterize experimental outcomes.

Prediction of transition metal oxide BO2(B = Ti, V, etc.) polymorph energetic properties is critical to tunable material design and identifying thermodynamically accessible structures. Determining procedures capable of synthesizing particular polymorphs minimally requires prior knowledge of their relative energetic favorability. Information concerning TiO2polymorph relative energetic favorability has been ascertained from experimental research. In this study, the consistency of first-principles predictions and experimental results involving the relative energetic ordering of stable (rutile), metastable (anatase and brookite), and unstable (columbite) TiO2polymorphs is assessed via density functional theory (DFT). Considering the issues involving electron–electron interaction and charge delocalization in TiO2calculations, relative energetic ordering predictions are evaluated over trends varying Ti Hubbard U3dor exact exchange fraction parameter values. Energetic trends formed from varying U3dpredict experimentally consistent energetic ordering over U3dintervals when using GGA-based functionals, regardless of pseudopotential selection. Given pertinent linear response calculated Hubbard Uvalues, these results enable TiO2polymorph energetic ordering prediction. Hybrid functional calculations involving rutile–anatase relative energetics, though demonstrating experimentally consistent energetic ordering over exact exchange fraction ranges, are not accompanied by predicted fractions, for a first-principles methodology capable of calculating exact exchange fractions precisely predicting TiO2polymorph energetic ordering is not available.

Systematic prediction of the redox reaction energetics of large sets of 3d transition metal oxides is imperative to the selection of oxygen carrier candidates in applications ranging from chemical looping to solid oxide fuel cell (SOFC) cathode design. In particular, the energetic study of oxygen vacancy formation in unmixed perovskites with La, alkali, and alkaline A-site metal cationsas well as 3d transition metal B-site cationsis a crucial first step in understanding the energetic tunability afforded by cation doping in ABO3materials. An assessment of the relative oxygen vacancy formation energetics of LaBO3, SrBO3, and similar materials that serve as a guideline for predicting energetics in related systems is completed below using density functional theory (DFT). This assessment illustrates which simplifications can be made in the prediction of energetics trends without affecting trend order. The independent consideration of oxygen vacancy concentration, crystal structure, and antiferromagnetic (AFM) magnetism revealed that these factors in DFT calculations had no effect on trend order. However, the ferromagnetic (FM) SrBO3trend order was affected between SrMnO3and SrFeO3as a function of defect concentration. Moreover, energetic trends were also formed by adding constant, incremental values of the Hubbard Uparameter contributing to the 3d orbitals of perovskite B-sites. Calculation of Uparameters was done by linear response theory or by a literature review of previous research.