Size/Strain Analysis for TOF data

kunyang

Dear All,

I have some questions on the Size/Strain Analysis for TOF data. I'm doing strain analysis, now I'm interested in peak broadening which due to crystal size and microstrain effect.
There is a topic "Size/Strain in topas" in the website
http://community.dur.ac.uk/john.evans/topas_workshop/size_strain.htm
It used LVol_FWHM_CS_G_L, but it seems the equation it used here is for CW data analysis but not TOF. Can I directly use it for TOF analysis?

Another question is:
Can the macro "strain_L" and "strain_G" be directly used for TOF analysis? It seems they were written on the basis of strain broadening equation in CW data. According to Balzar et al, J. Appl. Cryst. (2004), 37, the line-broadening formulas for CW and TOF are different, do I have to write a new macro for the Size–strain line-broadening analysis for TOF data? Is there anyone have similar experience? Thank you for all help.

Regards,

alancoelho

Kunyang

See TOF_CS_L and TOF_CS_G in TOPAS.INC

Also, see test_examples\tof_balzar_sh1.inp and tof_balzar_br1.inp. The latter uses the TOF_CS_L and TOF_CS_G parameters to obtain LVol.

Cheers
Alan

johnsoevans

There's also a tutorial based on the same data online via one of my topas/jedit pages.

kunyang

Thank you very much @Alan and John

Yes, I've read the test_examples\tof_balzar_sh1.inp and tof_balzar_br1.inp before, as well as the TOPAS.INC.
But in my understanding, here the macros TOF_CS_L and TOF_CS_G just describe Lorentzian and Gaussian components for crystallite size, not for microstrain, am I right?

If I want to analyse both crystallite size and microstrain, should I introduce the Strain_L and Strain_G?

alancoelho

Hi kunyang

Thanks for clarifying.

>Can the macro "strain_L" and "strain_G" be directly used for TOF analysis?

No as they apply to CW data. From my quick scribbles and from Braggs law and for CW x-rays we get:

delte_d/d = Tan(Th) delta_Th

The Strain_L and Strain_G macros are similar except delta_Th is in degrees and hence the Strain_L and Strain_G parameters need to be multiplied by Pi/180 to get delta_d/d.

In TOF refinement we have:

tof = t1 d

where t1 is the TOF calibration constant. Or,

delta_d/d = delta_tof / tof

where Xo is the reserved parameter name that returns the x-axis position of peaks which for TOF data is tof.

You should double check the above and also with someone that does the double Voigt strain work with tof data. Thus to exactly match Strain_L we would have:

macro TOF_Strain_L(c, v)
{
#m_argu c
If_Prm_Eqn_Rpt(c, v, min .0001 max 5111)
lor_fwhm = CeV(c,v) (Pi/180) Xo;
}

A data set with known strain would clarify things.

Hopefully someone can cross check the above.

Cheers
Alan