Structural, Electronic, Dynamical, and Superconducting Properties in Dense GeH₄(H₂)₂

Hydrogen-rich materials have fascinating physical and chemical properties such as various structures and superconductivity under high-pressure. In this study, structural, electronic, dynamical, and superconducting properties of GeH 4 (H 2 ) 2 are investigated based on the first-principles calculations. We first predict several phase transitions of GeH 4 (H 2 ) 2 under pressure. Below 28 GPa, two degenerated structures with I 4̅ m 2 and Pmn 2 1 symmetries are preferred, which can be viewed as the distortion of the experimentally observed fcc structure. Then, the GeH 4 (H 2 ) 2, via a triclinic phase that stabilizes in the pressure range of 28–48 GPa, transforms into a metallic orthorhombic phase in which appears the metallization induced by pressure. Another metallic phase with P 2 1 / c symmetry enters the phase diagram at around 220 GPa, which is more stable than the case of a decomposed material, and its stability is also confirmed by including the zero point energy correction. In the high-pressure P 2 1 / c phase, the superconductivity is found, and the superconducting transition temperature is predicted to be as high as 76–90 K at 250 GPa. This superconductivity mainly results from the local vibrations of more H 2 units, though the vibration of Ge in an H 2 -formed grid also contributes to the electron–phonon interaction. This study is helpful for understanding the superconducting mechanism on hydrogen-rich compounds.