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To design a high-performance Cu–Ti intermetallic coating, first-principles calculation is conducted to systematically investigate the phase stability, mechanical and electronic properties of the Cu–Ti binary intermetallics. The phase stability and mechanical properties are studied by calculating the formation enthalpy and independent elastic constants, respectively. The calculated formation enthalpy indicates that β-Cu 4 Ti, CuTi and CuTi 2 are stable phases at 0 K, while α-Cu 4 Ti, Cu 3 Ti, Cu 3 Ti 2 , and Cu 4 Ti 3 are metastable phases. In addition, the mechanical properties of Cu–Ti intermetallics present a positive correlation with their formation enthalpy. The electronic structures of the Cu–Ti intermetallics are evaluated by analyzing the bonds character to reveal the bonding characteristics, which is crucial to the phase stability and mechanical properties. Among the Cu–Ti intermetallics studied, CuTi phase exhibits the highest stability, hardness and a higher brittleness among all Cu–Ti intermetallics, while other Cu–Ti intermetallics show good toughness. Based on the calculated results, a high strength Cu–Ti intermetallic coating consisting of hard CuTi particles on a ductile Cu 4 Ti 3 matrix is proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The site preference of N in Cr2N is studied by a first principles method. [•] Theoretic elastic properties of Cr2N are obtained. [•] Mechanical characteristics of Cr2N are predicted. [•] Density of states reveals the origin of the stability and elastic properties. [Copyright &y& Elsevier]

Abstract: Carbon and nitrogen are the most frequent foreign interstitial atoms in α-Fe. The presence of even a little amount of these impurities in interstitial positions has a drastic influence on the properties of steels. However, the physics of the C–N interaction remains unclear. Here we perform first-principles calculations based on the density functional theory to study the interactions of C–N and those with vacancy (□) in α-Fe. When C and N atoms are in neighbor octahedral sites, a hybridization around −8eV of C 2p states with the N 2p states is observed. C and N atoms lie as far away from one another as possible. When a vacancy is introduced, it can attract two C atoms and a N atom, and a C–C–N–□ complex is formed. When the C and N atoms are the first nearest neighbors of the vacancy and stay in two neighbor octahedral sites, a covalent C–N bond is formed. And the peak of 2p states of the C atom’s density of states shifts to around −8eV, where the peak of the N atom’s 2p states lies. [Copyright &y& Elsevier]