Dear friends and colleagues The size of coherently reflecting domains, also known as crystallites, is important issue for nano structures.
I used GSAS-II to calculate the domain sizes. I used uniaxial domain size model and got equatorial =18.6 (1) nm axial 21.7 (2) nm. These values are higher compared to other tools: GSAS (Dv=12), STEM (12(3)) or Debye function analysis (Da,b=13.7 (5.0) nm, Lc=14.0(5.7) nm). Any idea what's wrong? The procedure I used to calculate the domain size at GSAS-II was as follows: LaB6, NIST Standard Reference Material (SRM) 660a, was first analyzed to define to instrumental parameters. In the phase data I used 2 micron for domain size and 330 for microstrain. (I also tried used 5 micron for domain size and 1 for microstrain). I used these values as in the certification of the SRM 660a it was stated that Rietveld analysis of the XRD data gave 2 micron for domain size and no strain broadening. (SEM analysis indicated that the particles of LaB6 consist of aggregates of crystallites; the size of the crystallites was in the 2 to 5 micron range). The instrumental parameters were refined. Later I analyzed my data using the instrumental parameters I got from the LaB6 standard, without refining that instrumental data. Instead I refined the domain size and later microstrains of my phase. By the way in GSAS (GSAS1) I just used parameters Lx and Gp to calculate the size and Gu and Ly to calculate the microstrain. Thanks Victor
_______________________________________________ GSAS-II mailing list GSAS-II@mailman.aps.anl.gov https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii
