So........ if you intend to start your analysis by using Atoms, you have to find the COMPLETE crystallographic data. Often, this is one of the more difficult parts of the analysis problem. Sometimes crystallography data is hard to find. Matt keeps a big pile of atoms.inp files on one of his web sites and that helps a lot. Many libraries have copies of Wyckoff -- that also helps a lot. Google can be awfully handy -- indeed I ended up finding the missing crystallographic data earlier today with the help of Google. Often times you will be reduced to an exhausting search through the crystallography journals looking for the data you need. Other times you will never find what you are looking for and will just have to use something similar (but not the same) as your starting point.
I'd add that the ICSD (inorganic crystal structure database) has just about every inorganic crystal structure ever published (more than 70,000). For a personal license, it's just 300 euro (although they charge you again every year or so to keep your subscription current with new structures). If you don't want to go that route, they offer a "demo" version online which has a randomly selected 4% of their database. 4% is actually pretty good, since many materials have had their structures determined multiple times (for example, someone doing a pressure series may include in their paper a re-determination of a known structure). The url is http://icsd.ill.fr/icsd/ --Scott Calvin Sarah Lawrence College