Issue 20, 2011

Substitutional and orientational disorder in organic crystals: a symmetry-adapted ensemble model

Abstract

Modelling of disorder in organic crystals is highly desirable since it would allow thermodynamic stabilities and other disorder-sensitive properties to be estimated for such systems. Two disordered organic molecular systems are modeled using a symmetry-adapted ensemble approach, in which the disordered system is treated as an ensemble of the configurations of a supercell with respect to substitution of one disorder component for another. Computation time is kept manageable by performing calculations only on the symmetrically inequivalent configurations. Calculations are presented on a substitutionally disordered system, the dichloro/dibromobenzene solid solution, and on an orientationally disordered system, eniluracil, and the resultant free energies, disorder patterns, and system properties are discussed. The results are found to be in agreement with experiment, when some physically implausible configurations are removed from the ensemble average for eniluracil, highlighting the dangers of a completely automated approach to organic crystal thermodynamics which ignores the barriers to equilibration once the crystal has been formed.

Graphical abstract: Substitutional and orientational disorder in organic crystals: a symmetry-adapted ensemble model

Supplementary files

Article information

Article type
Paper
Submitted
28 Jan 2011
Accepted
25 Mar 2011
First published
15 Apr 2011

Phys. Chem. Chem. Phys., 2011,13, 9590-9600

Substitutional and orientational disorder in organic crystals: a symmetry-adapted ensemble model

M. Habgood, R. Grau-Crespo and S. L. Price, Phys. Chem. Chem. Phys., 2011, 13, 9590 DOI: 10.1039/C1CP20249A

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