DASH: a program for crystal structure determination from powder diffraction data

Abstract

DASH is a user-friendly graphical-user-interface-driven computer program for solving crystal structures from X-ray powder diffraction data, optimized for molecular structures. Algorithms for multiple peak fitting, unit-cell indexing and space-group determination are included as part of the program. Molecular models can be read in a number of formats and automatically converted to Z-matrices in which flexible torsion angles are automatically identified. Simulated annealing is used to search for the global minimum in the space that describes the agreement between observed and calculated structure factors. The simulated annealing process is very fast, which in part is due to the use of correlated integrated intensities rather than the full powder pattern. Automatic minimization of the structures obtained by simulated annealing and automatic overlay of solutions assist in assessing the reproducibility of the best solution, and therefore in determining the likelihood that the global minimum has been obtained.

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption

“…The diffraction pattern was indexed using DICVOL91 44 to a monoclinic cell [F(18) = 71.0, M(18) = 19.8] and space group P2 1 /n was assigned from volume considerations and a statistical consideration of the systematic absences. The data set was background subtracted and truncated to d = 2.795 Å (2θ = 17.00°), for Pawley refinement 45 and the structure was solved ab initio using the simulated annealing (SA) global optimization procedure implemented in the DASH computer program 46,47 . The SA structure solution involved the optimization of four independent fragments in the asymmetric unit (one Cu atom, two Cl atom and one pyimH ligand), totalling 16 degrees of freedom.…”

Cocrystals of Fenamic Acids with Nicotinamide

“…22 Rietveld refinement was completed using the EXPGUI interface to GSAS. 23 Bond lengths and angles were restrained to values taken from the known crystal structures of the starting materials.…”

Identification of mixed bromidochloridotellurate anions in disordered crystal structures of (bdmim)2[TeX2Y4] (X, Y=Br, Cl; bdmim=1-butyl-2,3-dimethylimidazolium) by combined application of Raman spectroscopy and solid-state DFT calculations

“…In order to evaluate the structural consistency between a bulk powder and the single crystals subjected to structure analysis, peak indexing of the diffraction patterns were made using Pawley fitting method [36] in program DASH 3.2 [37]. Truncated data range of 6-45 ° and the unit cell settings of the corresponding single crystal structure were used as a starting point for the refinement of each pattern.…”