A first principles investigation was made of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and isostructural AlB2 within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions were calculated for both systems. The main differences were related to high frequency in-plane B vibrations, which were strongly softened in MgB2 and exhibited exceptionally strong electron-phonon coupling. Raman measurements were also reported which supported the theoretical findings.

Phonon Dispersion and Electron-Phonon Coupling in MgB2 and AlB2. K.P.Bohnen, R.Heid, B.Renker: Physical Review Letters, 2001, 86[25], 5771-4