You (and we) will not get the most out of your experiment if you are not properly prepared. You should consider the following issues carefully before you arrive. Talk to your local contact if you have any doubts.

Sample

• If the crystal volume is smaller than in your proposal or less than 1 mm3 per 1000A3 - tell your local contact at least 4 weeks before the experiment, and consider whether to postpone or cancel the experiment.
  
  
• Choose the compound and solvent carefully. Avoid if possible (mixed) organic solvents - high H content - which may give disorder complicating or preventing refinemnt
  
  
• Check the effect of cooling (or heating): phase transitions, cracking,
  
  
• Select at least 3 suitable crystals (or fibres...): quality,size, shape...
  
  
• How to mount a crystal  NYA
  
  
• Determine the dimensions of the 3 best crystals: perpendicular distance from an arbitrary internal origin to each plane face.  If this is not done, attempt on Huber optical goniometer at ILL before start of experiment.
  
  
• Index the faces e.g. on smart in home lab - this will avoid wasting neutron time doing it on d19 at start of the experiment.

Background information

• Refine the x-ray structure carefully - at the temperaure of the neutron expt if possible  - anisotropic TF's, solvent, non-controversial H atoms (yes !)
  
  
• calculate neutron F**2 for hkl's up to e.g. 2-theta=80 at e.g. 1.31A. You can even sort them on F**2 with Unix sort command: -e.g. sort -r +3 -4 unsorted.fcf -osorted.fcf
  where unsorted.fcf is the fcf file from shelxl with header stuff removed
  
  
• e-mail F**2 list and e.g. *.ins or xtal input file to your local contact
  
  
• Check the ILL web page at wwwold.ill.fr, for info on telnet connection, etc
  
  
• Learn a few basic Unix commands; we use an editor such as nedit (or vi ugh!)