Towards solution and refinement of organic crystal structures by fitting to the atomic pair distribution function
- Goethe Univ., Frankfurt am Main (Germany)
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States)
In this study, a method towards the solution and refinement of organic crystal structures by fitting to the atomic pair distribution function (PDF) is developed. Approximate lattice parameters and molecular geometry must be given as input. The molecule is generally treated as a rigid body. The positions and orientations of the molecules inside the unit cell are optimized starting from random values. The PDF is obtained from carefully measured X-ray powder diffraction data. The method resembles `real-space' methods for structure solution from powder data, but works with PDF data instead of the diffraction pattern itself. As such it may be used in situations where the organic compounds are not long-range-ordered, are poorly crystalline, or nanocrystalline. The procedure was applied to solve and refine the crystal structures of quinacridone (β phase), naphthalene and allopurinol. In the case of allopurinol it was even possible to successfully solve and refine the structure in P1 with four independent molecules. As an example of a flexible molecule, the crystal structure of paracetamol was refined using restraints for bond lengths, bond angles and selected torsion angles. In all cases, the resulting structures are in excellent agreement with structures from single-crystal data.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC00112704
- OSTI ID:
- 1240708
- Report Number(s):
- BNL-111879-2016-JA; ACSAD7; R&D Project: PM032; KC0202010
- Journal Information:
- Acta Crystallographica. Section A, Foundations and Advances (Online), Vol. 72, Issue 1; ISSN 2053-2733
- Publisher:
- International Union of CrystallographyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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