The bond structure of MgB2 with different lattice constants

We report a detailed study of the electronic structure of the MgB2 with different lattice constants by using the full-potential linearized augmented plane wave(FPLAPW) method. It is found that the lattice parameters have great effect on the σ band of Boron. Our results indicate that increasing lattice constant along the c axis will increase the density of states(DOS) at the Fermi level, making the σ band upward shift, and increasing hole number in the σ band. So, the superconducting transition temperature Tc will be raised correspondingly. Changing the lattice constant along a axis has an opposite effect to that of along c axis. Our result is in agreement with experiment. A possible way of searching for higher Tc superconductor has been indicated, i.e., making MgB2 to have longer c axis and shorter a, b axis by doping. PACS Number : 74.25.Jb, 74.70.Ad