IMAGING OF DIFFRACTION DATA BY MEM. Makoto Sakata, Dept. of Applied Physics, Nagoya University, Nagoya 464-01 JAPAN.

The recent works of charge and nuclear densities in crystalline materials using the Maximum Entropy Method (MEM) is reviewed. Recently MEM has been introduced and developed as a new method for accurate structure analysis^1,2). The MEM is promising in material science since the high resolution density distribution can be obtained directly from the limited number of diffraction data. The concept of Imaging of Diffraction Data is introduced to describe the role of MEM analysis in these works. Assuming that the phase problem is solved by direct method or some other way, it is possible to reconstruct real space image, such as the electron density distribution in the case of X-ray diffraction²⁾, the nuclear density distribution in the case of neutron diffraction³⁾, or the spin density distribution in the case of polarized neutron diffraction⁴⁾, directly from the experimental diffraction data. This process can be done without using any crystal structure model. This fact may provide a new approach in crystallography, in which all the sophisticated analyses, such as multipole or topological analysis⁵⁾ of charge density and anharmonicities in nuclear density⁶⁾ can be done based on the real space images of diffraction data instead of the reciprocal quantities of structure factors.

Reference

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5 B.B.Iversen et al.(1995) Acta Cryst. B51,580-591.

6 M.Takata et al.(1994) Acta Cryst. A50, 330-337.