ChrisW wrote:But going back to the orginal point, what is the best way to correlate crystal morphology to the unit cell contents and would this be viable in this case to try and compare structural failure of the crystal to the molecular packing environment?
Are you thinking about some sort of shear plane? Which allows your structure to cleave?
You may also access that kind of effect by straining the crystal with temperature. If it is a weak point then it just needs the correct motivation.
So relating structure to the crystal there are a couple of ways to do that.
An easy one is to stick the crystal on the OD/Nonius Kappa and get the unit cell (no DAC) then do face indexing. You can now relate the crystal morphology to the unit cell and you already know the unit cell contents and how they relate to the structure. From this you can tell that if the crystal cleaves along a particular direction and that direction relates back to a VdW or weak packing interaction etc.
Does that make any sense?
Also you could try cleaving a crystal on the microscope and see if it reproducibly breaks in the same direction.
If it was me I would:
- Smush some of my nice crystals under the micrscope with a big blunt scalpel blade to see if they repeated cleave and or break in a similar direction
- Glue mount a crystal to a tip - glue mount as you want to use the glued side to strain the crystal in the next step
- Do a variable temperature study on the crystal remembering to take good video/photos to look for evidence of changes and to cross reference any peak splitting in the diffraction against the images.
To disprove the phase change do a powder high pressure study as if it just the material cleaving but not changing into a new form the powder pattern will tell you. May also be possible to do a Raman experiment with powder if no X-ray diffraction available. On your OD you can do powder data but use FIT2D to convert the images to powder patterns, etc.