• Overall values of conventional discrepancy indices for crystals with heavy atoms. Part II. Results for monoclinic and orthorhombic crystals when the heavy-atom part alone constitutes the model

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      https://www.ias.ac.in/article/fulltext/pram/016/04/0295-0308

    • Keywords

       

      Theoretical evaluation; conventionalR-indices; monoclinic crystal; orthorhombic crystal; heavy atoms

    • Abstract

       

      Theoretical expressions of 〈yN〉, 〈|yN − σ1yPc |〉 and 〈|yN2σ12 (yPc)2|〉 (whereyN andyPc are the normalized structure amplitudes of the structure and the model respectively) are derived in terms of the heavy atom contributionσ12 for monoclinic and orthorhombic crystals containing a few (i.e., 1 or 2) heavy atoms of the same kind per asymmetric unit by taking the heavy atom part alone as the model. Results are obtained for both the related and unrelated cases. The local values of 〈yN〉 and 〈|yNn − σ1n (yPc)n|〉, (n=1, 2) calculated from these expressions can be used to calculate the overall values of the conventionalR-indicesR(F) andR(I) for the related and unrelated cases. These overall values could be used to check the correctness of heavy atoms located in the structure.

    • Author Affiliations

       

      S Parthasarathy1 M N Ponnuswamy1

      1. Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Madras - 600 025, India
    • Dates

       
  • Pramana – Journal of Physics | News

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