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 MgB2 and BeB2. Carefully comparing their band structure at different volumes and the corresponding phonon frequencies for the E2g 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 pseudopo?? tential 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 E2g phonon frequencies, electron-phonon coupling, valence-band top deformation potentials at different volumes, and Grüneisen parameters. Our results compare well with available experimental measurements.