Influence of pressure on the structural, elastic and thermodynamic properties of α- and β- PtAl high temperature alloys

Abstract

Although PtAl alloy is a promising high-temperature material, the mechanical properties and thermodynamic behavior of PtAl alloy under high pressure is entirely unknown. To solve this problem, here, we apply the first-principles calculations to study the influence of high pressure on the structural stability, mechanical and thermodynamic properties of PtAl alloy. Here, the α-PtAl and β-PtAl alloys under high pressure are selected. The calculated results show that α-PtAl has better thermodynamic stability in comparison to β-PtAl under pressure. Whether zero pressure or high pressure, this α-PtAl is a dynamical stability, in while the β-PtA is a dynamical instability. Although the elastic constants and elastic modulus of two PtAl alloys increase with increasing pressure, the ductility of two PtAl becomes better. Importantly, it is found that the calculated shear modulus and Young's modulus of α-PtAl are higher than the β-PtAl under high-pressure. Naturally, the high elastic modulus of PtAl is demonstrated by the change of Pt–Al bond under high-pressure. With increasing pressure, the bond length of Pt–Al bond becomes shorter whether α-PtAl or β-PtAl. Finally, it is found that the calculated Debye temperature (θD) of α-PtAl is higher than the β-PtAl under high pressure.