A First-Principles Modeling of the Elastic Properties and Generalized Stacking Fault Energy of Ir-W Solid Solution Alloys.

Iridium, with its excellent high-temperature chemical inertness, is a preferred cladding material for radioisotope batteries. However, its inherent room-temperature brittleness severely restricts its application. In this research, pure Ir and six Ir-W solid solutions (Ir(31)W(1) to Ir(26)W(6)) were modeled. The effects of W on the elastic properties, generalized stacking fault energy, and bonding properties of Ir solid solution alloys were investigated by first-principles simulation, aiming to find a way to overcome the intrinsic brittleness of Ir. With the W concentration increasing from 0 to 18.75 at %, the calculated Cauchy pressure (C(12)-C(44)) increases from -22 to 5 GPa, Pugh's ratio (B/G) increases from 1.60 to 1.72, the intrinsic stacking fault energy reduces from 337.80 to 21.16 mJ/m(2), and the unstable stacking fault energy reduces from 636.90 to 547.39 mJ/m(2). According to these results, it is predicted that the addition of W improves the toughness of iridium alloys. The alloying of W weakens the covalency properties of the Ir-Ir bond (the ICOHP value increases from -0.8512 to -0.7923 eV). These phenomena result in a decrease in the energy barrier for grain slip.