Preparing data for Pawley fitting of free water

samira11

Hello all,
I am trying do a pawley fitting for free water in my paste sample. I collected an XRD pattern of a paste that has 50 wt% water mixed with 50 wt% corundum. I wanted to remove the contribution of the corundum from my diffractogram from the water+corundum diffractogram with appropirate scale factor and then do a pawley fit on the difference plot. I found how to output difference plot I have not found yet how to actually remove the contribution of corundum. Should I include the corundum patter as bkg file and then do some scale adjustment and then output the difference plot?

johnsoevans

It's not clear what you are trying to do from this post. A Pawley fit would normally only be performed on a crystalline phase (unless you're trying the type of approach in section 5.8.3. of the Rietveld book).

However, in general, the difference plot will be everything you're not currently fitting, so would have the corundum contributions subtracted.

samira11

Thank you for your reply. Apologies for not being clear. Yes, I am trying the approach in the 5.8.3 of the book, trying the PONCKS method for modelling free water and amorphous powders such as slag. I wanted to mainly model the free water as a phase via pawley fitting. I was mainly asking how subtraction of XRD signals is done in TOPAS academic. I thought of somehow removing the crystal peaks of corundum by subtraction of corundum diffractogram from 50:50 water+corundum diffractogram with appropriate scale factor and get the amorphous hump, which then I would do the pawley fitting on.