Actinium hydrides $AcH_{10}$, $AcH_{12}$, $AcH_{16}$ as high-temperature conventional superconductors

TL;DR

This study predicts stable actinium hydrides with high-temperature superconductivity, demonstrating Tc up to 251 K at high pressures, and suggests a trend among d1-elements and p0-HTSC hydrides in forming such superconductors.

Contribution

The paper predicts new stable actinium hydrides with high Tc and provides insights into their structure and superconducting mechanisms, expanding the understanding of actinium-based high-temperature superconductors.

Findings

Actinium hydrides are predicted to be stable and superconducting at high pressures.

Predicted Tc ranges from 199 K to 251 K depending on the phase and pressure.

Structural and electron-phonon interactions support phonon-mediated high-temperature superconductivity.

Abstract

Stability of numerous unexpected actinium hydrides was predicted via evolutionary algorithm USPEX. Electron-phonon interaction was investigated for the hydrogen-richest and most symmetric phases: R$\overline{3}$m-$AcH_{10}$, I4/mmm-$AcH_{12}$ and P$\overline{6}$m2-$AcH_{16}$. Predicted structures of actinium hydrides are consistent with all previously studied Ac-H phases and demonstrate phonon-mediated high-temperature superconductivity with Tc in the range 204-251 K for R$\overline{3}$m-$AcH_{10}$ at 200 GPa and 199-241 K for P$\overline{6}$m2-$AcH_{16}$ at 150 GPa which was estimated by directly solving of Eliashberg equation. Actinium belongs to the series of d1-elements (Sc-Y-La-Ac) that form high-Tc superconducting (HTSC) hydrides. Combining this observation with p0-HTSC hydrides ($MgH_{6}$ and $CaH_{6}$), we propose that p0- and d1-atoms with low-lying empty orbitals tend to form phonon-mediated HTSC metal polyhydrides.