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Keywords:

  • Rietveld refinement;
  • Morse bond energy potential;
  • bond restraints

A new restraint scheme for Rietveld refinement based on Morse bond energy potential is introduced, in which the asymmetry of the Morse potential allows the refinement to `break' the incorrectly placed bonds. The analysis of bond-length distributions at different values of restraint strength reveals a visible difference in behavior of wrong and correct structures, which can be detected using robust statistical methods. This fact is employed as a basis for a novel structure verification criterion. The approach is demonstrated on known difficult cases of acetolone and γ-quinacridone and used for the Rietveld refinement of N-(6-phenylhexanoyl)glycyl-L-tryptophanamide, an organic molecule of a potential anxiolytic containing 32 non-H atoms and 14 single bonds. The results are verified using density functional theory calculations with periodic boundary conditions.