MgB2 and BeB2: A comparative study of their electronic and superconducting properties

We report a detailed study of the electronic and dynamical properties of superconducting MaB(2) and BeB2. Carefully comparing their band structure at different volumes and the corresponding phonon frequencies for the E-2g mode, we are able to explain their very different superconducting behavior in terms of different electron-phonon coupling. Our calculations are performed within the local-density approximation to the density-functional theory, using the full-potential linearized augmented plane wave and plane-wave pseudopotential in order to calculate phonon frequencies with frozen-phonon approach and linear-response theory, respectively. Our results highlight differences and similarities between the two compounds and give information regarding the zone center E-2g phonon frequencies, electron-phonon coupling, valence-band top deformation potentials at different volumes, and Gruneisen parameters. Our results compare well with available experimental measurements.