Electronic and structural properties of MgB2 by the linear combination of atomic orbitals method

In this paper theoretical calculations of electronic and structural properties, namely Compton profiles and structure factors of MgB2, are presented. The calculations are performed using periodic linear combination of atomic orbitals method. Exchange and correlation has been treated under the Perdew-Wang generalized gradient approximation (PW-GGA) and the hybrid Becke-3-Lee-Yang-Parr (B3LYP) schemes. The Compton profiles at 15, 55, and 293 K are calculated by considering only the thermal expansion of the lattice keeping all other computational parameters identical. The calculated Compton profiles have been compared with the published experimental data measured using synchrotron radiation. The calculated profiles under the PW-GGA scheme are well in accordance with the measurements. The best agreement at the level of first and second order derivatives of Compton profiles has, however, been found with the B3LYP hybrid function. In the superconducting state the momentum density shows sharper changes than the normal state around Fermi momentum. The structure factors for a number of reflection lines have also been computed and compared with the published electron diffraction and the synchrotron x-ray powder diffraction data. The calculations are found to be in good agreement with the measurements. The calculation supports the charge transfer from Mg plane (001) to the (002) plane containing boron atoms, well in agreement with the prediction of the measurement.