Structural stability, mechanical, and thermodynamic properties under pressure of B2-type CuM (M = Be, Al, and Zn) alloys: a DFT investigation

Abstract In this work, we systematically examined the structural stability, mechanical properties, and thermodynamic behavior of B2-type CuBe alloy, and compared the results with isostructural Cu-based alloys (CuAl and CuZn) by employing first-principles calculations in the pressure range of −22 to 100 GPa. This study revealed the stable existence of CuBe alloy at low-density expansion states (e.g. ∼ −20 GPa), indicating its superior structural stability compared to CuAl and CuZn. The pressure dependence of properties such as cell parameter a ( a / a 0 ) and density ρ ( ρ / ρ 0 ), elastic parameters (elastic constants C ij , bulk modulus B , shear modulus G , and Young's modulus E ), deduced parameters ( B / G ratio, Poisson's ratio ν , Vickers hardness, sound velocity, and Debye termperature Θ D ), and thermodynamic parameters (free energy F , entropy S , and heat capacity C v ) were investigated. All Cu M ( M = Be, Al, and Zn) alloys had more difficulty undergoing uniaxial stress than shear stress. External pressure reduced the ductility of the CuBe alloy, while excess pressure ( P > 50 GPa) resulted in increased ductility, which was similar to CuAl but different from CuZn. The hardness and Θ D values demonstrated consistent variation corresponding to the ductility changes. Thermodynamic parameters were minimally affected by pressure, and the stronger interactions led to greater F in the CuBe alloy. These findings offer confidence for the future design of ordered Cu-Be alloys with exceptional properties.