Pressure-induced Evolution Of Hydrogen Dissolution And Superconductivity In Solid Solution Of Rhenium

Looking for high-temperature superconductors is always the hot issue in the field of condensed matter physics.And the initial theoretical prediction-the superconducting transition temperature?T_c?of metallic hydrogen would be 100K⁷00 K at high pressure is always the subject for researchers to prove.However,the metallization pressure and the evolution path of hydrogen are still controversial due to the limitation of experimental conditions.In 2004,Ashcroft suggested the addition of other chemical elements to hydrogen would lead to“chemical pre-compression”in the lattice of hydrogen,which could make it metallized at lower pressure and show high temperature superconductivity similar to metallic hydrogen.Subsequently,hydrogen-rich compound materials under high pressure are extensively studied by scientists.And high T_c in SH₃ and LaH₁₀0 have been confirmed by experimentally.In these high-pressure experiments of hydride-rich and superhydride compounds,rhenium is often used as gasket material because of its high bulk elastic modulus?370GPa?and low brittleness.Initial hydrides may decompose and release H atoms dissolving into Re gasket to form Re-H solid solution in such related experiments,which has been studied in some experiments.But the microscopic aspects?e.g.electronic properties,superconducting mechanisms,et al.?of rhenium hydrides are rarely explored in theory.So,based on the first-principle calculation,we systematically explored the properties of Re-H solid solution under high pressure from microcosmic level.In the pressure range of 1⁵0 GPa,we explored H solubility in rhenium that related to the increasing pressure,and calculated the crystal structure,electronic properties,lattice dynamic characteristics and electron-phonon coupling of Re-H solid solutions by ab initio method.Six stable solid solutions with different ratio between Re and H atoms are predicted,and the solubility of H in rhenium increases with increasing pressure.Compared with elemental rhenium,the symmetry of Re substrate for each H-doped compound remains unchanged with H dissolved in the interstitial sites.Electron density of states at Fermi surface and electron local function analysis show that all of the six Re-H solid solutions exhibit metallicity and strong ionicity.And the electrons transfer from Re atom to H atom.We then explored the effects of H solubility in rhenium on the superconductivity of Re-H solid solutions.Since the mass of H atom is very small,the increasing H solubility in rhenium improves the phonon frequency of the solid solutions.In addition,the electron density of states N??_F?at the fermi surface of the Re-H solid solutions is mainly contributed by Re atoms,and electrons transfer from Re atoms increase with increasing H solubility,which leading to the decrease N??_F?of solid solution.Finally,the increasing phonon frequency and the decrease of N??_F?result in the decrease of electron-phonon coupling constant?and superconducting transition temperature T_c of Re-H solid solutions accompany with increasing H solution.We further clarify the effects of hydrogen content on superconductivity of metal-base hydrides,and our findings would be benefit to explore the new type of superconductive hydrides.