Atomic-level investigations of adsorption behavior of 1H- benzotriazole (BTAH) on Al surface are presented. Combination of reactive molecular dynamics method with experimental measurements is used for describing behavior of BTAH layer on oxide-coated Al surface upon contact with chloride-containing solution at 298 K. A thick BTAH layer formed on Al surface consists of two regions, a pseudo-monolayer at the BTAH/oxide interface and a loosely packed layer with randomly oriented BTAH molecules at the BTAH/aqueous solution interface. Physical adsorption dominates over chemisorption of BTAH to oxide-coated Al surface. Corrosion inhibition by a self-assembled BTAH layer was discovered. A protective action by the self-assembled layer was first detected by EIS data and then supported with analysis of electrochemical parameters by using equivalent electrical circuit (EEC) model to observe a strong capacitive behavior. Dissolution of BTAH layer becomes a critical factor controlling its inhibition action caused by weakening of intermolecular hydrogen bonding between BTAH molecules. Al-Cl bonds formed confirming pitting corrosion occurrence on oxide-coated Al surface. An increase in surface roughness with increasing immersion times was also observed for unmodified Al as well as for BTAH-modified Al surface.

Oxidation phenomena on metal surfaces can be advanced using atomistic modeling for the study of the structure and properties of the growing oxide films. Molecular dynamics investigations were performed to study thermal oxidation of single-crystal and polycrystalline Al–Mg alloys with low Mg content of up to 2.5 at. %. Structure, topological atom network and surface topography of the oxide films grown on Al–Mg surfaces at 300, 475 and 663 K are determined. Mg-content and temperature dependent oxide films developed on Al-Mg alloy substrates with two-phase oxide film formation as also confirmed experimentally. It is related with a gradual long-range order formation above 475 K for (Al,Mg)-oxide films, for which solid amorphous phase predominates over crystalline phase. The 1.12-nm-thick oxide films grown at 300 K are fully amorphous and build up from (Al, Mg)-oxide which the Al2O3 dominates. Increase of Mg coefficient confirms faster Mg diffusion to oxide/alloy interface at high oxidation temperature and the formation of MgO-like network. The presence of planar crystal defect (grain boundary, GB) into Al-Mg alloy substrate governs the kinetics of oxide film growth and its structure evolution. GB also compensate internal stresses during oxide film growth. Obtained results are in good agreement with experimental observations.

For the Cu(100), Cu(110), and Cu(111) surfaces varying asymmetric line shapes are found for the atomic 3d⁸4s² multiplet two-hole final state binding energies reached in MVV Auger photoelectron coincidence spectroscopy. Higher asymmetry for Cu(111) and Cu(110) in comparison to Cu(100) is caused by reduced dynamic screening for Cu(111) and Cu(110) in contrast to free electron like Cu(100). This is a consequence of the surface projected band gaps in Cu(111) and Cu(110) not present in Cu(100). We describe the distinct tailing in the experimental line shapes of the three Cu surfaces with first principles calculations of layer-dependent two-hole binding energy shifts, depth-dependent intensity distribution and Doniach-Sunjic asymmetry parametrization. These fundamental insights into the surface-specific electronic structure can advance the understanding of structure-reactivity relationships in Copper-based surfaces and catalysts.

Reliable long-term creep rupture life prediction of high-temperature materials demands a deep understanding of rupture-controlling mechanisms. Conventional analytical models for creep rupture extrapolation rely heavily on experimental data and adjustable parameters, potentially neglecting the critical failure mechanisms. This study employs fundamental creep models for HR3C(25Cr20NiNbN) austenitic steels, incorporating ductile and brittle creep mechanisms with well-defined physical parameters and no adjustable parameters. The ductile creep models account for dislocation hardening, precipitation hardening, solid solution hardening, and stacking faults, while the brittle creep models in addition consider creep cavitation along sliding grain boundaries. Key physical parameters are derived as follows: precipitate evolution is simulated using thermodynamic computations and validated against experiments, while high-temperature elastic properties and atomic-size misfit are determined through first-principles calculations, with lattice vibrations incorporated via the quasi-harmonic Debye model. By combining first-principles and thermodynamic calculations, the mechanism-based fundamental models successfully predict the creep rupture strength of HR3C quantitatively.

In-situ small-angle neutron scattering (SANS) experiments, with and without an applied magnetic field of 1.5 T, were performed for two duplex stainless steels: 22Cr-5Ni and 25Cr-7Ni (wt.%) during isothermal heat treatment at 450 ∘C. The kinetics of phase separation was suppressed by the external magnetic field in both steels; however, the suppression was much more pronounced in 25Cr-7Ni, where phase separation was nearly eliminated. The difference in magnetic energy contributions from the external field in each steel explain their different degrees of phase separation. The findings are believed to have large technical implications for mitigating low-temperature embrittlement in Fe-Cr-Ni based alloys.

Grain boundary sliding (GBS) significantly influences the mechanical properties of polycrystalline metals and alloys. A comprehensive set of GBS data spanning 70 years and encompassing 12 material classes under various deformation conditions has been compiled. Analysis identifies strain (ε) and grain size (dg) as the primary factors influencing GBS displacement in agreement with a previously developed basic model, revealing a linear dependence of GBS displacement on strain and grain size. A major factor in the model is the strain enhancement factor, i.e., the ratio between the creep strain due to GBS and the total creep strain. Utilizing the average strain enhancement factor from the GBS data (0.2), the model demonstrates predictive capabilities across various materials (Fe, ferritic steels, austenitic steels, Al, Mg, Cu, Zn, and their respective alloys), grain sizes (nanometers to micrometers), and strain levels (0.1–161 %) without significant loss in statistical accuracy. Application to creep cavitation further illustrates the usefulness of the model.

The dissolution behavior of tungsten carbide (WC) particles in liquid cobalt is investigated using ab initio and classical molecular-dynamics calculations. It turns out that at the atomic level there is a complex interplay between surface properties, bulk diffusion, and dissolution. It is found that carbon-rich shells form around dissolving WC particles, creating a semidissolved state. The dissolution process is decelerated by trapping carbon atoms via the formation of carbon-carbon bonds, both on the surface of dissolving particles and in the surrounding semidissolved shell. Upon reaching a critical particle radius, the dissolution rate sharply increases, driven by changes in the number of carbon-carbon bonds, resulting in a premelting behavior. The existence of a semidissolved shell and premelting behavior advance our understanding of dissolution mechanisms at the atomic scale and can be applicable for controlling dissolution processes that are an important part of coarsening of WC particles, a phenomenon taking place during cemented carbide manufacturing.

The full description of the mechanisms for the diffusion of substitutional impurities requires an account of the correlation of the atomic jumps. This study investigated the diffusion of phosphorus (P) and sulfur (S) in the fcc copper (Cu) single crystal using density functional theory (DFT). Vacancy formation energies and impurity–vacancy interactions were calculated, revealing attractive interactions of P and S with the vacancies. The attractive interactions between S and a vacancy were roughly twice as strong as those between P and a vacancy. The 5-frequency—or 5-jump—model was employed to describe the correlation effects during diffusion. The potential energy profiles and activation energies were determined for the different jump paths necessary for the model and to account for all the correlation effects in substitutional impurity diffusion in the single crystal. The results indicated that S diffuses significantly faster than P in Cu, primarily due to lower activation energies for certain jump paths and a more favorable vacancy–impurity interaction. This occurs because when bonding with the crystal, S tends to prefer atomic sites with larger volumes and more asymmetric geometric arrangements when compared to P. This favors the interactions between S and the vacancies, and reduces friction with the matrix during the diffusion of S. The effective diffusion coefficients were calculated and compared with experimental data. The findings provide insights into the diffusion mechanisms of P and S in Cu and how these can be affected by the presence of extended defects such as grain boundaries.

A combinatorial approach is employed to investigate the atomic and electronic structures of a metal vacancy in titanium carbide. It turns out that the usual relaxed geometry of the vacancy is just a metastable state representing a local energy minimum. Using ab initio calculations and by systematically searching through the configurational space of a Ti monovacancy, we identify a multitude of local minima with reconstructed geometry that are lower in energy. Among them, there is a planar configuration with two displaced carbons forming a dimer inside the vacancy. This structure has the optimal number and order of C-C bonds making it the global minimum. Further calculations show that this reconstructed geometry is also the ground state of metal vacancies in other carbides such as ZrC, HfC, and VC. The reconstructed metal vacancies are characterized by localized electron states due to the relatively short C-C bonds. The defect states lie just below the upper and lower valence bands. The existence of reconstructed vacancy configurations is essential for understanding the mechanism of metal self-diffusion in transition-metal carbides.

Materials design and performance prediction relies on detailed knowledge of the distribution of solutes that can affect the materials properties. Here we report a study on the distribution and mechanisms of interaction of S and P atoms at four relevant grain boundaries (GBs) of fcc Cu: Σ3, Σ5, Σ9 and Σ11. Segregation site preference was investigated for single atoms and compared to the case where impurities segregate as pairs. Both the driving force for segregation—local minima—and the interactions between impurities at the GBs—global minima—have been investigated. An analysis of geometric and electronic structure effects in segregation was performed. Single S-atoms bind more strongly to GB sites than single P-atoms. For all GBs the driving force for segregation decays fast with distance from the planes and reaches the bulk values already at ≈ 4 Å. In the near vicinity of the GBs, with increased concentration, the interactions between S-atoms are mostly attractive, while for the same sites the interactions between P-atoms are mostly repulsive. S-atoms are capable of displacing P-atoms and the accumulation of P is not favorable at the GB planes, while the accumulation of S is favorable. We also performed geometric and electronic structure analyses using symmetry quantifying indicators and developed a descriptor of electronic structure effects called “impurity projected density of states (DOS)” for analyzing the bonding between the impurities and the Cu matrix. Overall, segregation is favored by an increase in the asymmetry of the segregation sites. S binds more asymmetrically to those sites preferring an off-center position while P-atoms bind more symmetrically adopting a central position. At GBs with the same excess volume, S-atoms bind stronger than P-atoms and fitting functions that describe these trends were obtained. The balance between bonding states, antibonding states, and the covalent contributions to the bonding between the impurities and the copper matrix are at the origin of the observed preferences.