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Theoretical Study of Electronic Structure and Superconductivity in Nb_(1-x)B_2 Alloys
Using the Korringa-Kohn-Rostoker coherent-potential approximation in the
atomic-sphere approximation (KKR-ASA CPA) we have studied the changes in the
electronic structure and the superconducting transition temperature T_{c} in
Nb_{1-x}B_{2} alloys as a function of x. We find that the variation in the
electronic structure of Nb_{1-x}B_{2} alloys as a function of x is consistent
with the rigid-band model. However, the variation of T_{c}, 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 \omega_{rms} in the
Allen-Dynes equation over the whole range of vacancy concentration, thereby
indicating the importance of lattice dynamical effects in these systems.Comment: 10 pages, 4 figure