A full-potential LAPW study of structural and electronic properties of beryllium

Abstract

The authors present self-consistent band-structure calculations of HCP Be made by means of the full-potential linearised-augmented-plane-wave (LAPW) method and on the basis of the local density approximation. In contrast to earlier calculations no shape approximations for the charge density or the potential are made and all electrons are taken into account. From the full charge density, X-ray form factors are calculated that agree very well with recent experimental data. This indicates that the significant deviations between experiment and earlier calculations are due to strong muffin-tin- effects. The electric field gradient (EFG) is very sensitive to the quality of the theoretical calculation. In earlier theoretical work not even the sign of the EFG could be determined unambiguously. Within the authors formalism the EFG is determined directly from a given charge density without any approximations. Starting with a muffin-tin potential the EFG is found to be 15 times larger than experiment. The present full-potential LAPW calculation, however, yields an EFG in good agreement with experiment. From calculations at different lattice constants it is found that the EFG depends strongly on the c/a ratio but only weakly on the volume. The equilibrium lattice parameters are determined by total-energy minimisation and agree with experiment within 2%.