Density Functional Theory Applied on MgB2
Jui Wen Chou1*
1Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
* Presenter:Jui Wen Chou,
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