Origin of strong coupling in lithium under pressure

In an attempt to provide a clearer understanding of the impressive increase in T-c under pressure in elemental Li, linear response calculation of the phonon dispersion curves, electron-phonon matrix elements, phonon linewidths and mode lambda's have been carried out on a finer mesh (24(3) in the Brillouin zone) than done previously, for the volume corresponding to 20 GPa pressure. The result illustrates the great need for a fine mesh (even finer than this) for converged results of A and the spectral function alpha F-2. Although the initial pressure-induced transverse I-1 phonon instability (in harmonic approximation) near the symmetry point K has dominated attention, the current results show that the high value of T-c gets strong contributions from elsewhere in the zone, particularly from the longitudinal mode along (100). (c) 2007 Elsevier B.V. All rights reserved.