JOURNAL OF FACULTY OF ENGINEERING & TECHNOLOGY, Vol 22, No 1 (2015)

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BUILDING PRIOR DENSITIES FOR MAXIMUM ENTROPY REFINEMENT OF X-RAY DATA FOR TOPOLOGICAL ANALYSIS

Ahmad Shuaib, Abdul Waheed Anwar, Khurshid Aslam Bhatti, Ishrat Mubeen Dildar, Qasim Ali Chaudhary

Abstract


The aim of this research work is to develop a method to provide a reasonable “prior” electron density that can be used in the so-called “Maximum Entropy Method” (MEM) refinement of X-ray diffraction (XRD) data in order to reconstruct experimental electron density at a resolution allowing its accurate topological analysis. A program was developed which build electron density on a regular grid in the “Independent Atom Model” (IAM) approach, more precisely from the knowledge of individual “spherical” atomic scattering factors of the atoms constituting the unit cell of the studied compounds. IAM X-ray structure factors of bismuth and its prior density on a grid has been generated to be tested with the MEM “Enigma” software. Preliminary accuracy and performances have been compared when such reasonable “prior” density is used instead of starting with “flat” density.  


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Faculty of Engineering & Technology

University of the Punjab

Lahore-54590-Pakistan