Charge-density distribution of Be metal studied byγ-ray diffractometry

With a $\gamma$-ray diffractometer, eight extinction-free structure factors for beryllium have been measured on an absolute scale with an accuracy of about 0.5%. These data are in good agreement with another recent measurement by Larsen and Hansen using x rays, but in serious disagreement with an earlier set of x-ray data due to Brown. The $\gamma$-ray structure factors are compared with results of SCF-HF-LCAO (self-consistent-field, Hartree-Fock, linear combination of atomic orbitals) and APW (augmented-plane-wave) band-structure calculations. Theoretical and experimental structure factors are in reasonable agreement except for the two lowest-order reflections. A significant improvement of the APW results may be obtained by going beyond the muffin-tin approximation. Renormalized-free-atom and OPW (orthogonalized-plane-wave) model calculations show that the structure factors are sensitive to the average form of the wave functions, whereas Compton profiles mainly depend on the orthogonality of the wave functions.