First-principles investigation of pressure-induced variation in the structural and physical properties of ternary high-Tc superconductor LaBeH8

Abstract

A conspicuous ternary hydride Fm-3m-LaBeH8 superconductor with the particular Be-H alloy backbone was initially predicted in theory and subsequently synthesized in experiment with the measured superconducting critical temperature Tc of 110 K under the moderate pressure of 80 GPa. Nevertheless, previous investigations mainly aimed at deciphering its structural characteristics and superconductivity, few explorations involves other physical and chemical properties, which is invaluable for its practical application. Herein, on the basis of the first-principles calculation, we comprehensively inquire into the structural, bonding, mechanical, electronic, superconductive, thermophysical and optical properties for the cubic Fm-3m-LaBeH8 structure under various pressures ranging from 20 to 120 GPa. The bonding essence in Fm-3m-LaBeH8 is theoretically predicted as the ionic La-H bond and the synthetic Be-H bond with the ionic and covalent character. Moreover, the cubic Fm-3m-LaBeH8 crystal is predicted to be thermodynamically, mechanically and dynamically stable within the considered pressures. A linear increase with the increasing pressure in elastic constants (C11 and C12) and bulk modulus B is achieved. More interestingly, shear modulus G and Young's modulus E undergo a distinct and complicated variation process upon further compression, which is similar with those of elastic constant C44, transverse and mean sound velocities, Vickers hardness Hv and Debye temperature θD. The remarkable superconductivity originates from the high hydrogen-dominated electronic density of states around the Fermi energy and the overriding hydrogen contribution to electron-phonon coupling strength. Notably, the high superconducting critical temperature Tc in the cubic Fm-3m-LaBeH8 configuration stems from the combined effect of λ and ωlog. In addition, Fm-3m-LaBeH8 is an underlying absorbing material for the violet and UV lights. These findings raise the understanding of the grand superconductivity and the remaining physical properties of the LaBeH8 superconductor, greatly stimulating its synthesized enthusiasm for experimental researchers and broadening its practical space.