Wang Gao1*

1Key Laboratory of Automobile Materials, Ministry of Education, Department of Materials Scienceand Engineering, Jilin University

 EXTENDED ABSTRACT: The surface and interface stability of metallics depends on the bonding properties of surface and interface atoms, which play an essential role in corrosion, solid-solution strengthening, and heterogeneous catalysis. Therefore, it is of great significance to quantitatively predict the bonding characteristics of surface and interface atoms and uncover their quantitative relationship. Several conventional models, such as d-band theory and broken-bond models, have been proposed to predict surface and interface stability. However, they are mainly suitable for transition metals but are hardly applicable to complex alloys, and some of these conventional models predict with low accuracy. Therefore, we have proposed novel descriptors to characterize the adsorption energy, the surface energy, the surface-site ejection energy, and the segregation energy of solutes at the grain boundary. We have established an intrinsic model of the adsorption energy of small molecules, demonstrating that the adsorption energy is mainly determined by the valence-electron number, electronegativity and coordination number of the active sites of surface atoms and the valence properties of the adsorbate. This model lays a solid foundation for the theoretical and experimental design of advanced materials with specific adsorption properties, such as catalysts and sensors. We have also designed some potential alloy catalysts by combining the intrinsic model and machine learning. In addition, we have developed novel models to determine the surface energy and surface-site ejection energy of metallics, which reveals the intrinsic determinants of the surface stability, clarifies the differences and connections of the bonding characteristics between different alloys, uncovers the coupling relationship between the adsorption energy, surface energy and the surface-site ejection energy, and provides an effective method to rapid screening materials with good stability and corrosion resistance. Furthermore, we have also uncovered the general principles of the solute segregation at the grain boundary. The segregation of the solutes at the grain boundaries of metal single crystal and polycrystal is determined by the valence-electron number, electronegativity, and size of the solute atom and the coordination number of free surfaces. This model clarifies the alloying effect of solutes and matrices, draws a novel physical picture of solute segregation at the grain boundary, and can serve as an effective tool for designing high-performance alloys. Overall, these models based on the intrinsic descriptors are applicable to determine the surface and interface stability of various metallics, particularly of complex high entropy alloys, which have a solid fundamental basis. Their good prediction ability can effectively support the development of corrosion-resistant, solid-solution-strengthening, and adsorption-functional materials.

Keywords:Surface and interface stability; Intrinsic descriptors; Theoretical models; Heterogenous catalysis; Corrosion and solid-solution strengthening