First-Principles Calculation for the Electron--Phonon Coupling Constant of Superconducting MgB₂

We use a first-principles plane wave method with the new relativistic analytic pseudopotential of the Hartwigsen, Goedecker and Hutter (HGH) scheme and the pseudopotential of the Troullier--Martins scheme to calculate the electron--phonon coupling constant λ of superconducting MgB₂. The calculated results show that there is a peak at about 300-350cm^-1 in the electron--phonon spectral functional α²F(ω), duo to the coupling of the electrons to the acoustic phonon, and the relativistic effect appears in the high frequencies zone. All the results agree well with the present and previous experimental data.