Theoretical study of electronic structure and superconductivity in Nb1-xB2 alloys

Using the Korringa-Kohn-Rostoker coherent-potential approximation in the atomic-sphere approximation we have studied the changes in the electronic structure and the superconducting transition temperature T-c in Nb1-xB2 alloys as a function of x. We find that the variation in the electronic structure of Nb1-xB2 alloys as a function of x is consistent with the rigid-band model. However, the variation of Tc, obtained using the Allen-Dynes equation within the Gaspari-Gyorffy formalism to estimate the electron-phonon matrix elements, does not follow the expected trend. We associate this disagreement to the use of a constant in the Allen-Dynes equation over the whole range of vacancy concentration, thereby indicating the importance of lattice dynamical effects in these systems. (C) 2003 Published by Elsevier B.V.