Using first-principles calculations based on density functional theory, the elastic constants and some of the related physical quantities, such as the bulk, shear, and Young’s moduli, Poisson’s ratio, anisotropic factor, acoustic velocity, minimum thermal conductivity, and Debye temperature, are reported in this paper for the hexagonal intermetallic compound Ti ${}_3$ Al. The obtained results are well consistent with the available experimental and theoretical data. The effect of pressure on all studied parameters was investigated. By the mechanical stability criteria under isotropic pressure, it is predicted that the compound is mechanically unstable at pressures above 71.4 GPa. Its ductility, anisotropy, and Debye temperature are enhanced with pressure.

The surface composition of an alloying system has an important impact on its catalytic and chemical properties.

Segregation at metal alloy surfaces is an important issue because many electrochemical and catalytic properties are directly correlated to the surface composition. We have performed density functional theory calculations for Mo segregation in MoNi(111) in the presence of chemisorbed atomic oxygen. In particular, the coverage dependence and possible adsorption-induced segregation phenomena are addressed by investigating segregation energies of the Mo atom in MoNi(111). The theoretical calculated results show that the Mo atom prefers to be embedded in the bulk for the clean MoNi(111), while it segregates to the top-most layer when the oxygen coverage is thicker than 1/9 monolayer (ML). Furthermore, we analyze the densities of states for the clean and oxygen-chemisorbed MoNi(111), and see a strong covalent bonding between Mo d-band states and O p-states. The present study provides valuable insight for exploring practical applications of Ni-based alloys as hydrogen evolution electrodes.

Surface adsorption and dissociation processes can have a decisive impact on the catalytic properties of metal alloys. We have used density functional theory to investigate the adsorption and dissociation of O₂ on Cu-skin Cu₃Au(111) surface. The calculated results show that the b-f(h)-b adsorption configuration is the most energetically favorable on the Cu-skin Cu₃Au(111) surface. For O₂ dissociation, there are two thermodynamically favorable dissociation paths. One path is from b-f-b to two O atoms in hcp sites, and the other path is from b-h-b to two O atoms in fcc sites. Moreover, the stability of O₂ adsorption is higher and the dissociation energy barrier of the adsorbed O₂ is lower as compared to those on the Cu(111) surface. This theoretical work provides valuable guidance for the practical application of Cu-Au alloys as highly efficient CO oxidation catalysts.

The elastic, mechanical, acoustic, and thermal properties of ${\mathrm{Ti}}_3$Si${\mathrm{C}}_2$, ${\mathrm{Ti}}_3$Ir${\mathrm{C}}_2$, and ${\mathrm{Ti}}_3$Au${\mathrm{C}}_2$ MAX phases were systematically investigated using first-principles calculations based on density functional theory. The computed lattice parameters and elastic, mechanical, and acoustic properties were consistent with existing experimental and theoretical findings, confirming the intrinsic mechanical stability of these MAX phases. Single-crystal elastic stiffness constants were used to derive polycrystalline elastic moduli, directional dependencies of bulk, shear, and Young’s moduli, and anisotropic factors. The results revealed a ductility sequence of ${\mathrm{Ti}}_3$Si${\mathrm{C}}_2$ < ${\mathrm{Ti}}_3$Ir${\mathrm{C}}_2$ < ${\mathrm{Ti}}_3$Au${\mathrm{C}}_2$, with ${\mathrm{Ti}}_3$Ir${\mathrm{C}}_2$ and ${\mathrm{Ti}}_3$Au${\mathrm{C}}_2$ exhibiting greater elastic anisotropy than ${\mathrm{Ti}}_3$Si${\mathrm{C}}_2$. Additionally, sound velocities, Debye temperatures, minimum thermal conductivities, melting points, and Grüneisen parameters were determined. The findings showed that ${\mathrm{Ti}}_3$Si${\mathrm{C}}_2$ outperforms ${\mathrm{Ti}}_3$Ir${\mathrm{C}}_2$ and ${\mathrm{Ti}}_3$Au${\mathrm{C}}_2$ in sound velocity, average sound velocity, Debye temperature, and minimum thermal conductivity, while ${\mathrm{Ti}}_3$Ir${\mathrm{C}}_2$ has the highest melting point and ${\mathrm{Ti}}_3$Au${\mathrm{C}}_2$ the largest Grüneisen parameter. These results provide valuable insights into the design of related materials for high-performance applications.

The O₂ dissociative adsorption serves as a pivotal criterion for assessing the efficacy of oxygen reduction catalysts. We conducted a systematic investigation into O₂ dissociative adsorption on the Pt-skin Pt₃Cu(111) surface by means of the density functional theory (DFT). The computational findings reveal that the O₂ adsorption on Pt-skin Pt₃Cu(111) surface exhibits comparatively lower stability when contrasted with that on the Pt(111) surface. For O₂ dissociation, two paths have been identified. One progresses from the t-f-b state towards the generation of two oxygen atoms situated within nearest-neighbour hcp sites. The other commences from the t-b-t state, leading to the generation of two oxygen atoms occupying nearest-neighbour fcc sites. Moreover, the analysis of the energy barrier associated with O₂ dissociation indicates that O₂ on the Pt-skin Pt₃Cu(111) surface is more difficult to dissociate than on the Pt(111) surface. This study can offer a valuable guide for the practical application of high-performance oxygen reduction catalysts.