Dear Franziska

There are loads of examples and tutorials for TOPAS and TOPAS Academic at the TOPAS wiki (http://topas.dur.ac.uk/topaswiki/doku.php?id=topas) as well as from John Evans (http://community.dur.ac.uk/john.evans/topas_workshop/topas_user_menu.htm).

I remember also a tutorial from Arnd Kern (CONVOLUTION BASED PROFILE FITTING)  from the 2011th TOPAS User Meeting. 

Regards 

Dominique

Dear Franziska

Just add a couple more after you read the link from Dominic. Here one of the method in Topas:

1. Load your standard reference material (SRM) data

2. Insert the .CIF for that particular SRM

3. Select Structure > Peak type > change to other except FP (First Principle))

4. Select Structure > Microstructure > change crystal size L to ~ 1500 (LVol-IB ~950 nm) > change to Fix

5. Instrument > check Simple Axial model > change to Refine

6. Run

When you load your sample, fix all the refine paramater in Peak Type that you've choosed then release the Crystal size L.

U can do the the same with GSAS, MAUD, Fullprof etc.

I preferred PM2K (WPPM) to do this job. Simply refine the Caglioti formula (u,v,w,a,b,c) to parameterise the instrumental profile component from SRM scan. Then Fix it to refine the actual sample broadening.

Please find the project file (Bruker TOPAS) for size strain evaluation using instrumental broadening.