Elastic properties of platinum Rh and Rh3X compounds

Platinum metal Rh-base alloys present promising candidates as future ultra-high-temperature gas turbine materials due to their excellent high-temperature properties. In this Letter, ab initio density functional theory (DFF) calculations have been performed to determine the elastic constants of face-centered cubic platinum metal Rh and its L1(2) intermetallic compounds Rh3X (X = Ta, Ti, Nb, V, Zr, Hf). The calculated elastic constants of Rh are compared to those from experimental observations and other theoretical calculations using tight-binding (TB), linear augmented planewave (LAPW) and model pseudopotentials approaches. The calculated elastic constants are then used to estimate mechanical properties of Rh and Rh3X compounds. The brittle/ductile behavior is assessed by analyzing the phenomenological formula G/B of shear modulus (G) over bulk modulus (B) and the Cauchy pressure (C-12-C-44). As a gamma/gamma' two-phase material, the gamma' (Rh3X) precipitation strengthening effect in the gamma (Rh) matrix is examined from the difference in shear modulus A G between the two phases. The elastic properties of Rh-base alloys are compared to those of Ir-base alloys. The new knowledge from this study could be used for future development of Rh-base alloys. (C) 2004 Published by Elsevier B.V.