Prediction of Superconductivity in Clathrate Er Hydrides under High Pressure

Abstract

In this paper, we perform unbiased structure searches combined with first-principles calculations to predict the stable structures and possible superconductivity of ErHn (n = 4~6) under pressures of 50~300 GPa. Two novel compounds, ErH4 and ErH6, are identified as thermodynamically and dynamically stable above 50 GPa; ErH4 and ErH6 can stabilize in clathrate structures with the I4/mmm and Im3¯m space groups, respectively. An analysis of the electronic density of states (DOS) suggests the metallic nature of the two phases. Then, the superconducting critical temperature (Tc) is estimated using the Allen–Dynes modified McMillan equation; the results are 130.9~181.2 K for Im3¯m-ErH6 at 100~300 GPa, and 74.4~79.8 K for I4/mmm-ErH4 at 150~300 GPa. The resultant high Tc superconductivity in this system can be traced back to the combination of high density of states at the Fermi level and strong electron–phonon interactions.

Keywords

• superconductivity
• clathrate structure
• high pressure
• metal hydrides