Effects of Disorder in Mg_{1-x}Ta_{x}B_2 Alloys using Coherent-Potential Approximation

Abstract

Using Korringa-Kohn-Rostoker coherent-potential approximation in the atomic-sphere approximation (KKR-ASA CPA) method for taking into account the effects of disorder, Gaspari-Gyorffy formalism for calculating the electron-phonon coupling constant $\lambda$, and Allen-Dynes equation for calculating T_c, we have studied the variation of T_c in Mg_{1-x}Ta_{x}B_2 alloys as a function of Ta) concentration. Our results show that the T_c decreases with the addition of Ta for upto 40 at% and remains essentially zero from 60 at% to 80 at% of Ta. We also find TaB_2 to be superconducting, albeit at a lower temperature. Our analysis shows that the variation in T_c in Mg_{1-x}Ta_{x}B_2 is mostly dictated by the changes in the B p density of states with the addition of Ta.