Charge density analysis from complementary high energy synchrotron X-ray and electron diffraction data

To accurately measure the low order structure factors of alpha -Al2O3, two- dimensional convergent beam electron diffraction (CBED) data from parallel- sided platelets at various accelerating voltages, thickness and orientation s have been matched using the Bloch-wave method. Middle and high angle exti nction-free data has been obtained by the extrapolation of multi-wavelength synchrotron X-ray measurements to zero wavelength. The combination of high -energy synchrotron X-ray diffraction and CBED allows the extinction-free a bsolute-scale measurements and improves the reliability of the electron cha rge density maps in alpha -Al2O3. (C) 2001 Elsevier Science Ltd. All rights reserved.