Study on the relationship between uniaxial strain and critical transition temperature of MgB 2 based on first-principles

It has been indicated the critical transition temperature ( ) of MgB decreases with the increase of hydrostatic pressure, but this is a comprehensive change after the multiaxial strain, and the influence of strain on is not fully understood. In this paper, based on the McMillan superconducting calculation formula and the first-principles density functional theory, the change and the properties of MgB such as energy band, Fermi surface, differential charge density, and phonon dispersion under uniaxial strain were studied, and the relationship between uniaxial strain and these properties was analyzed. The calculated of MgB at zero strain was 38.35 K, which is in good agreement with the experimental value of 39 K. When the -axis strain was 1%, the value could increase to 49.7 K, and there was a further improvement trend. When the -axis compression strain was -1%, decreases to 31.52 K. When the -axis tension-compression strain was applied, the change of value was small. Further analysis showed that the impact of -axis strain on the differential charge density, electronic band structure, phonon dispersion, and other properties of MgB was significantly greater than that of -axis strain, and the influence of these properties on was discussed. The work in this paper has certain theoretical and guiding significance for preparing MgB with higher and the study of the effect of uniaxial strain on of superconducting materials.