Stable structures and properties of Ru₂Al₅

Abstract Novel ordered intermetallic compounds have stimulated much interest. Ru–Al alloys are a prominent class of high-temperature structural materials, but the experimentally reported crystal structure of the intermetallic Ru 2 Al 5 phase remains elusive and debatable. To resolve this controversy, we extensively explored the crystal structures of Ru 2 Al 5 using first-principles calculations combined with crystal structure prediction technique. Among the calculated x-ray diffraction patterns and lattice parameters of five candidate Ru 2 Al 5 structures, those of the orthorhombic Pmmn structure best aligned with recent experimental results. The structural stabilities of the five Ru 2 Al 5 structures were confirmed through formation energy, elastic constants, and phonon spectrum calculations. We also comprehensively analyzed the mechanical and electronic properties of the five candidates. This work can guide the exploration of novel ordered intermetallic compounds in Ru–Al alloys.