Subject:

**Peak shape**
Hi,

I am a quite new user of Topas and your answer will be very appreciated. I am using Topas 6 academic version.

To train myself I calculated an xrd pattern from a .cif file. I wanted to realize indexing, pawley fitting and eventually structure solution. I generated the xrd pattern by using 1.54056 Å wavelength.

I determined the space group and lattice parameters by indexing but when I do a Pawley fit I am getting a very low Rwp value. The peak positions are metching but the peak shape is not. Is it because I used the wrong instrumental parameters, which one would be the correct choice? Or do I need to change peak shape parameters in Pawley fit? Unfortunetly I have very limited understanding about peak shapes therefore I cannot ask more spesific questions.

I am a quite new user of Topas and your answer will be very appreciated. I am using Topas 6 academic version.

To train myself I calculated an xrd pattern from a .cif file. I wanted to realize indexing, pawley fitting and eventually structure solution. I generated the xrd pattern by using 1.54056 Å wavelength.

I determined the space group and lattice parameters by indexing but when I do a Pawley fit I am getting a very low Rwp value. The peak positions are metching but the peak shape is not. Is it because I used the wrong instrumental parameters, which one would be the correct choice? Or do I need to change peak shape parameters in Pawley fit? Unfortunetly I have very limited understanding about peak shapes therefore I cannot ask more spesific questions.