A First‐Principles Study on the Effect of Rh Content on the Lattice, Electronic and Mechanical Properties of Pt‐Rh Solid Solution

ABSTRACT Platinum (Pt) alloys are essential for extremely high‐temperature applications owing to their superior strength and oxidation resistance. Rhodium (Rh) is a critical alloying element, yet the atomistic mechanisms by which Rh content governs Pt‐based solid solution performance remain elusive. In particular, the effects of Rh on lattice distortion and electronic structure require clarification. Here, we systematically investigate Pt‐ x Rh ( x = 0–40 wt.%) using density‐functional theory (DFT) to reveal the influence of Rh content on structural, electronic, elastic, and thermal properties. The results show that increasing Rh enhances Young's and shear moduli while simultaneously intensifying mechanical anisotropy. Ideal tensile simulations indicate that higher Rh raises the elastic stress, reflecting strengthening associated with Rh‐induced lattice and bonding modifications. Electronic structure analysis confirms excellent metallic conductivity, with localized charge accumulation around Rh atoms leading to notable lattice distortions. Thermal analyses demonstrate that increasing Rh elevates the Debye temperature, reduces thermal expansion, and accelerates heat capacity saturation toward the Dulong–Petit limit. These findings provide fundamental insights into the role of Rh in Pt‐based solid solutions and offer valuable guidance for the rational design of high‐performance noble metal solid solutions for demanding high‐temperature applications.