Ab initio structure determination of the low-temperature phase of succinonitrile from laboratory X-ray powder diffraction data-coping with potential poor powder quality using DFT ab initio methods

P. S. Whitfield, Y. Le Page, A. Abouimrane, I. J. Davidson

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11 Citations (Scopus)

Abstract

Without experimental or predicted literature crystal structures for succinonitrile at low temperature, structure solution was attempted from powder diffraction data taken at 173 and 90 K from a solid sample. Its room-temperature plastic-crystal state makes production of a sample with good particle statistics and random orientation almost impossible. Combining constrained models, simulated annealing, and careful application of second-order spherical harmonic corrections nevertheless produced viable-looking structures at 90 and 173 K, yielding two distinct structure models with the same projection down c. VASP optimization of atom coordinates in the experimental cell agreed well with the 90 K model but poorly with the model derived from the 173 K data. The refined 90 K structure changed little on optimization and fitted all datasets from 85 to 225 K. Plots of cell data, torsion angles, and isotropic displacement parameters against temperature suggest possible phase transitions around 100, 120, and 180 K. Cell data at 90 K: monoclinic P21/a, a=9.0851 (5) Å, b=8.5617 (5) Å, c=5.8343 (3) Å, Β=79.295 (2) °, and Z=4. Succinonitrile has gauche conformation, in agreement with literature spectroscopy data.

Original languageEnglish
Pages (from-to)292-299
Number of pages8
JournalPowder Diffraction
Volume23
Issue number4
DOIs
Publication statusPublished - 11 Dec 2008

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Keywords

  • DFT methods
  • Nonambient diffraction
  • Simulated annealing
  • Structure solution

ASJC Scopus subject areas

  • Radiation
  • Materials Science(all)
  • Instrumentation
  • Condensed Matter Physics

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