Accurate measurement of the Si structure factor by the Pendellösung method

The X-ray structure factor of Si was measured for 30 net planes from the thickness dependence of the integrated intensity on the λ scale. In ten low-order planes, the accuracy level was estimated to be 0.05% in the probable error. Therefore, the deviation from the standard model of Hartree-Fock isolated atoms under harmonic oscillation could be determined with high precision. In the remaining net planes, the accuracy level was 0.1%. Dawson's rule (that even and higher-order reflections should be normal) was well satisfied for eight net planes higher than 660. Against this background, some Fg values of odd and middle-order planes deviate from the standard model. In the difference Fourier map, not only the bonding charge and the charge deficit in the anti-bonding region but also a slight excess near the atomic position were recognized.