Hydrogen Pentagraphenelike Structure Stabilized by Hafnium: A High-Temperature Conventional Superconductor.

Abstract

Recent discovery of H3S and LaH10 superconductors with record high superconducting transition temperatures, Tc, at high pressure, has fueled the search for room-temperature superconductivity in the compressed superhydrides. Here we introduce a new class of high Tc hydrides with a novel structure and unusual properties. We predict the existence of an unprecedented hexagonal HfH10, with remarkably high value of Tc (around 213-234 K) at 250 GPa. As concerns the novel structure, the H ions in HfH10 are arranged in clusters to form a planar “penta-graphene-like” sublattice. The layered arrangement of these planar units is entirely different from the covalent sixfold cubic structure in H3S and clathrate-like structure in LaH10. The Hf atom acts as a precompressor and electron donor to the hydrogen sublattice. This “penta-graphene-like” H10 structure is also found in ZrH10, ScH10 and LuH10 at high pressure, each material showing a high Tc ranging from 134 to 220 K. Our study of dense superhydrides with “penta-graphene-like” layered structures opens the door to the exploration of a new class of high Tc superconductors.