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Tutorials and Examples

Automated Single Crystal Structure Solution Using Sir2002

What to do if you have weak data that is causing Sir2002 difficulties - using a Rhomax cutoff

The CCP14 Homepage is at http://www.ccp14.ac.uk
[CCP14 Tutorials page] | [Sir97/2002 Tutorial Index] | [EXPO]
[WinGX] | [Crystals] | [Platon/System S]

Sir97 (and soon for Sir2002) can be spawned transparently from the following single crystal suites (freely available for students and academics) :

Note: a feature of Sir97 and Sir2002 that may not be obvious is that if it fails to solve on the first trial, you should just leave it run. Sir2002 by default goes through the first 200 Trials.

However, if your data is very weak or noisy, it may be best to use a Rhomax cutoff to tell Sir2002 not to use the superfluous noisy data.

Be wary that Sir2002 assumes you have put in the correct chemistry (or close to the correct chemistry). When in doubt, perform an elemental analysis. It is not that uncommon for other elements to be present in inorganic crystals, especially if a flux of different composition has been used to grow the crystals.

Obtaining the data

Click here to obtain the zipped veryfast data and Sir2002 starting file (this data is distributed with the Crystals software)

Putting a Rhomax cutoff into Sir2002

Copy over an existing Sir2002 *.sir file. Open the file in your favourite text editor and modify the cell, hkl file, spacegroup and contents information as per the following. By default, Sir2002 assumes F-square data. While the "Fosquare" command used in Sir97 is now redundant in Sir2002, it will not cause any harm having it in.

If you don't seem to get anywhere with the data, try adding a Rhomax cutoff into Sir2002 - as shown below. 

%window
%structure    veryfast
%init
%job   veryfast in C 2/c
%data
         Cell     15.610  13.121  16.353  90.000 100.623  90.000
         Space   C 2/c
         Content   C   192 H   128
         Rhomax    0.250
         Reflections   veryfast.hkl
         Format  (3i4,2f8.2)
         Fosquare
%continue

Now running Sir2002 with the Rhomax - solves on Trial 11

From the top left menu select, File, Load and Go. Select the *.sir file and then select the Go ICON. You can edit the information before trying to solve the structure by selecting the Edit ICON.

Where as Sir2002 may have had difficulties due to all the high angle weak data, it may now be able to solve the structure quite easily. In this case on Trial 11.

[CCP14 Tutorials page] | [Sir97/2002 Tutorial Index] | [EXPO]
[WinGX] | [Crystals] | [Platon/System S]
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