Bulk material is also poly-cristalline, so you calculate a powder pattern. However, bulk material is normally textured and if the sample is not uniform, the shape of the sample can influence your relative intensities, too. Refinement of lattice constants works, but atomic positions and occupation factors will be probably wrong.
I understand "bulk material" to be powdered material so you use powder... unless you managed to grow a giant single crystal in which case you use a single crystal diffractometer and different software (SHELXTL). I presume you have some kind of CIF (crystallographic information file) that you are using as the model structure?
As Matthias said, you can definitely get lattice constants. Atomic positions and occupation factors are harder to get right.
A few groups out there grind their samples for 30 minutes in mortar and pestle and take very long scans (8hrs +) to do refinement work.
Often the truth is in between. You material might be neither single crystalline nor fulfill the grain size requirement of a powder, i.e. below 1µm. Then you have certain problems which can also affect the peak positions since not exactly in the diffraction plane they are irregularly shifted (since cut by the detector aperture out of plane). Therefore, I would only partially agree with the opinion of Matthias and Erica. Maybe this is ment by "optimization"? Sorry, I do not use Fullprof... It is perhaps a better way to contact the authors directly.
I would agree with the opinion of Gert Nolze. The growth of the bulk single crystal is a big task.
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography