PreparationOfSingleCrystalData
If you have poor single crystal data then it may be possible to solve the structure within DASH using the simulated annealing protocol. This is often successful in cases such as limited hkl ranges from high pressure cells, or just poorly diffracting crystals which do not give enough data for direct methods phasing. DASH requires a file containing the h, k, l, F2 and(F2) values in the SHELX format and a molecular model. Once the hkl data have been read in, the structure solution proceeds as for powder diffraction.
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Select Preparation of single crystal data from the first DASH Wizard (see The DASH Wizard) and click Next >.
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Enter the crystal system, space group and unit cell parameters in the boxes provided:
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Click Next >.
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This window allows the maximum resolution of the data to be set. In most cases the default resolution of 1.75 Å will be appropriate:
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Click Next >.
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Open the file containing the h, k, l, F2 and (F2) values. The .hkl file is expected to be in SHELX format:
- There are three options available for processing the data, and in most cases it is appropriate to use the default values:
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Recalculate ESDs.
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Discard F2 lower than 2.0 sigma.
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Average Friedel related pairs.
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Click Next >.
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Enter the file name of an .sdi file where the information required for structure solution will be saved:
- This will bring up the DASH Wizard : Molecular Z-Matrices window. Proceed with entering a molecular model and setting up simulated annealing runs as for normal powder data (see Structure Solution).