Superconducting properties of hydride Eu2 XH6 (X = Fe, Ru, and Os)

Exploring high-temperature superconductivity holds great significance for physics, chemistry, and materials science. In this work, we systematically investigate the crystal structures, electronic and dynamical properties, and superconducting properties of the ternary hydrides Eu2XH6 (X = Fe, Ru, and Os) over a pressure range of 0–210 GPa using first-principles calculations. Under ambient pressure, Eu2FeH6 and Eu2RuH6 display half-metallicity, while Eu2OsH6 shows spin-polarized semiconducting behavior. The magnetic moment of the Eu atom is about 6.6 μB, and the magnetic ground states of the three kinds of Eu2XH6 are all ferromagnetic. The electron–phonon coupling calculations show that Eu2RuH6 exhibits a superconducting critical temperature (Tc) above 41 K at 180 GPa, Eu2FeH6 reaches Tc ≈ 18 K at 190 GPa, and Eu2OsH6 attains Tc ≈ 14 K at 40 GPa. Unlike many hydrogen-rich superconductors where hydrogen dominates the electron–phonon interaction, in Eu2XH6, the hydrogen contribution is relatively minor, with the main role played by Eu and transition-metal atoms and their vibrational modes. Moreover, in Eu2XH6, applying external pressure effectively enhances the electron–phonon coupling, thereby increasing the superconducting critical temperature. Therefore, our findings identify Eu-based ternary hydrides as promising candidates for realizing relatively high-temperature superconductivity under moderate pressures.