Density Functional Theory Applied on MgB₂

Jui Wen Chou^1*

¹Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Jui Wen Chou, email:lbr20002@gmail.com

By application of the density functional theory, we investigated how the topological properties influenced the Fermi energy, the free energy and the band structure of MgB₂. When fixed the lattice constants a and b, increased only the lattice constant c from 3.234 Å to 3.734 Å, the Fermi energy of the system decreased from 5.906 eV to 4.952 eV, the external pressure drop from 116.32 Kbar to -55.78 Kbar. The minimum free energy is found at c = 3.526Å when a = b = 3.073 Å. Based on Bardeen, Cooper and Schrieffer theory, the corresponding critical temperature is estimated to be 38.8 K. The critical temperature of the MgB₂ can be tuned from 75.2 K to 31.0 K. For the experimental critical temperature 39 K, according to our calculations, the estimated corresponding lattice constant c = 3.523 Å with external pressure 0.214 Kbar.

Keywords: the density functional theory, Bardeen, Cooper and Schrieffer theory, Fermi energy