Computational prediction of samarium hydride at megabar pressure

TL;DR

This paper predicts stable samarium hydride structures at high pressure using computational methods, explores their electronic and phononic properties, and assesses their potential for superconductivity around 200 GPa.

Contribution

It introduces new predicted stable phases of samarium hydrides at high pressure and combines multiple computational techniques to analyze their properties.

Findings

Proposes SmH₂ and SmH₆ as stable phases at high pressure.

Analyzes electron and phonon dispersions in samarium hydrides.

Evaluates potential for low-temperature superconductivity.

Abstract

Samarium hydrides, belonging to the broad class of lanthanide polyhydrides, have yet to be experimentally tested at high pressure. In this study, we use random structure searches to explore multiple possible stoichiometries and propose SmH$_2$ with a layered hexagonal structure in the $P6/mmm$ space group and SmH$_6$ with hydrogen clathrate structures in the Im-3m space group as theoretically stable phases of samarium hydrides at a wide range of pressures centered around $200$ GPa. We further combine the first-principles methods of density functional theory and dynamical mean-field theory to explore many-body correlations in samarium hydrides, reporting electron and phonon dispersions and densities of states, and also evaluate the electron-phonon driven superconductivity to investigate low critical temperatures at $200$ GPa.