A first-principles study of electron–phonon coupling in electron-doped LiH

Abstract

The electronic structure, lattice dynamics, and electron–phonon coupling (EPC) of electron (n)-doped LiH have been extensively studied using ab initio methods within the virtual crystal approximation. The overall agreement of the lattice constants and bulk modulus for pure LiH with the experiments is excellent if the zero-point motion is taken into account. From the theoretical calculation for n-doped LiH, it is indicated that metallic n-doped LiH might be a good superconductor. Moreover, the EPC parameter λ for n-doped LiH was found to increase with the dopant concentration, resulting from the softening of optical phonon modes and the increase of the electron density of states at the Fermi level, while a decreasing trend of λ was predicted for the presence of pressure. Phonon linewidth calculations suggested that the optical phonon mode makes the main contribution to the EPC. A possible mechanism for the predicted superconductivity of n-doped LiH has been discussed.

Impact of lattice vibrations on equation of state of the hardest boron phase

“…In theory, we take into consideration the lattice vibrations, often neglected in first-principles simulations. We show that the phonon contribution has a profound effect on the EOS of B 28 , giving rise to anomalously low values of the pressure derivative of the bulk modulus and greatly improving the agreement between theory and experiment. Boron is a unique element of the Periodic Table with very unusual structural and physical properties.…”

“…An accurate equation of state (EOS) is determined for the high-pressure orthorhombic phase of boron, B 28 , experimentally as well as from ab initio calculations. The unique feature of our experiment is that it is carried out on the single crystal of B 28 .…”

“…The unique feature of our experiment is that it is carried out on the single crystal of B 28 . In theory, we take into consideration the lattice vibrations, often neglected in first-principles simulations.…”

“…[12][13][14] High-pressure boron has orthorhombic symmetry, and its unit cell contains 28 atoms (B 28 ). The properties of B 28 are rather remarkable.…”

“…Indeed, the measured Vickers microhardness 58(5) GPa of the orthorhombic boron phase in an asymptotic-hardness region (load up to 10 N) is in the range of polycrystalline cubic boron nitride and makes B 28 the second hardest elemental solid after diamond. 15 An experimental equation of state (EOS) for the B 28 phase has been obtained in Refs. 15 and 16.…”