Size and strain - Rietveld/Pawley/Le Bail

eriksvenssongrape

Hi all,

I've been trying to set up a rigorous SOP for assessing line broadening due to size and strain, and I'm following the general procedure outlined in the Durham Topas tutorial (thank you Prof. Evans for all the good resources!).

After going through the recommended reading (Balzar, 2004, 10.1107/S0021889804022551) I arrived at a point where I am thinking about the need for a full Rietveld refinement for assigning peak broadening to size and strain, as opposed to a Pawley or Le Bail fit.

I apologize if I have missed something fundamental here (very likely), but does the need for a full structure refinement in tandem with size/strain analysis mainly stem from wanting to ensure a physically reasonable partition of reflection intensities? That is, to make sure that the fitting of the acquired powder pattern can reasonably be attributed to discrete crystalline phase(s) and that the intensities are reasonable?

Thankful for any help or guidance!

Best wishes,
Erik Svensson Grape
postdoc, University of Oregon and Uppsala University

PS. I would also love to hear if anybody has any good resources on Warren–Averbach analysis. DS.

johnsoevans

I don't think there's any need for Rietveld over Pawley/Le Bail. As you say, all the Rietveld will do is constrain the intensities according to the model. If there's not severe peak overlap then a structure-independent model should be fine.

eriksvenssongrape

Great, then I'll proceed with a structure-independent approach, at least for an initial comparison between different samples. Thank you for the reply!