Solutions for Week-1 exercices

1- A search in the JCPDS-ICDD PDF-2 database, after background subtraction and Kalpha2 elimination, by using the Socabim EVA software, with the constraint that La, Cr and O atoms should be present, shows that the sample could contain LaCrO4 (card N°36-0093). However, at this stage, either an impurity is mixed with LaCrO4, either the PDF-2 card is wrong since a lot of reflections are observed on the powder pattern and lacking on the card.

Then a general default search is performed, and it appears that the sample could be simply isotypical with LaVO4, of which the structure was determined (PDF-2 card N°70-2392, meaning that it is a calculated pattern coming from the ICSD database). Probably, there is a series of isotypical compounds there, including Ce(VO4), LaAsO4 and many others which are able to match the powder pattern as well, or more or less. This conclusion has to be confirmed by further study, of course, but in such a case, a direct try by using the Rietveld method starting with the LaVO4 atomic coordinates and cell parameters should allow to refine the structure of LaCrO4.


2- A default search shows that the white deposit is very probably calcium acetate hydrate :


3- Default searches or limited to mineral sub-data show that those geologists have come back with zeolite samples.

Sample3 is very probably chabazite :


Sample 4 is very probably laumontite :


Sample 5 is very probably natrolite :

Sample 6 seems to be a mixture containing chabazite. But the other phases are not easily identified. Maybe vermiculite and other one(s), not well crystallized (the search was restricted to the mineral sub-file) :