Amorphous Materials
For samples which are amorphous, use an analogous crystal structure, but don't include distant paths. For example, ordinary glass can be initially modeled as SiO2, or an amorphous, octahedrally coordinated Fe3+ compound as alpha-Fe2O3. In the latter example, you'll certainly want to include more than the first path, because both the nearest-neighbor oxygen atoms and the nearest-neighbor iron atoms can be roughly approximated by the alpha-Fe2O3 structure. But paths out at, say, 5 Angstroms are probably not useful if the material is highly amorphous.
When doing this, it is especially important to try fitting different sigma2 parameters for different shells, even in cases where you've found that it's not necessary for a crystalline sample you are using as a standard.
This page is part of CategoryNotBulkCrystals. Pages in this category give tips on using Artemis to analyze materials that are not simple macroscopic crystals.