Large number of reflections not 'explained'.Composition: A badly incorrect formula can throw out many direct methods programs some charge flipping programs are more resistant as they use Fs and not Es.Data: Weak(I/sigma(I) Having tried SHELX(S), SIR2004, (SUPER)FLIPPER(WinGX) etc to no avail and before badmouthing the chemist for really not trying, re-examine: As a first step, contact your supervisor to arrange training. If you wish to do the data collection yourself it would usually be at weekends. If the sample is toxic safe handling procedures should be indicated.īecause of the diverse and often unknown chemical, toxicological and radiological nature of the material, contaminated material, typically wipes and microscope slide(s), may be returned, as well as the residual 'crystals'. Fill in an application form CRS Application for X-ray Crystal Structure Determination giving chemical, structural, toxicological etc.Narrow bore vials, small numbers of small crystals, especially in excess mother liquor will make extraction difficult, as will screwtops, by introducing grooves at the top of the vial. Make your sample is 'available' ie extractable.As far as possible the sample should be pure.Where the crystals are only stable in their mother liquor, for preference the solvent(s) used should be as non-volatile as possible and non toxic, as the solvent will tend to evaporate during examination.Sufficient characterisation should be carried out to verify that, at least, the crystal is not starting material or a previous structure. 'Good' includes being of a reasonable size, 0.2-0.5mm (less if heavy elements are present), clear and uncracked with well defined edges and faces. The crystals should be produced as slowly as possible to increase the probability of 'good' crystals.
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