Theoretical Study of Electronic Structure and Superconductivity in Nb_(1-x)B_2 Alloys

TL;DR

This study uses theoretical methods to analyze how the electronic structure and superconducting transition temperature of Nb_{1-x}B_{2} alloys change with composition, highlighting the limitations of simplified models and the significance of lattice dynamics.

Contribution

It provides a detailed theoretical analysis of Nb_{1-x}B_{2} alloys' electronic and superconducting properties, emphasizing the role of lattice dynamical effects.

Findings

Electronic structure variation aligns with the rigid-band model.

Superconducting transition temperature trend does not match expectations.

Constant _{rms} assumption affects T_{c} predictions.

Abstract

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.