Setting up instrument corrections for data obtained Cobalt diffractometer

ben1980

Hi people,

Could anyone please tell me how I can set up instrument corrections for data obtained from Cobalt diffactometer

I got GSAS file for this diffractomer as below

INS BANK 1
INS DTYPE STND
INS HTYPE PXCR
INS 1 ICONS 1.7889 1.7915 0.0000 0.739 0 0.000
INS 1 IRAD 3
INS 1I HEAD dummy incident spectrum for Co Ka radiation
INS 1I ITYP 0 0.0000 180.0000 1
INS 1INAME D5000
INS 1PRCF1 3 19 0.00100
INS 1PRCF11 570.884950 -268.827800 48.632165 0.400000
INS 1PRCF12 11.898740 3.362627 0.005000 0.005000
INS 1PRCF13 0.000000E+000 0.000000E+000 0.000000E+000 0.000000E+000
INS 1PRCF14 0.000000E+000 0.000000E+000 0.000000E+000 0.000000E+000
INS 1PRCF15 0.000000E+000 0.000000E+000 0.000000E+000

Cheers

johnsoevans

If you use jedit then going through the menus for a simple Rietveld with "other diffractometer" plus reading the pdf document on LP factors on the main wiki should help.

John

ben1980

Hi John,

Thanks for your reply. I have checked other lab diffractometers but none of them seemed to fit my case here.

For example CoKa3.lam from emission profiles gives me

lam ymin_on_ymax 0.0001
Lam_recs
{
0.5981 1.788960 0.4700
0.0503 1.789879 0.3357
0.3516 1.792850 0.8052
}

I guess the above file is for Co instrument with three different wavelengths

However the Cobalt diffractometer I used seems to be CoKa1 with wavelength 1.7889.

Cheers

Ben

johnsoevans

Ben,

You can just delete the parts of the emission profile you don't want.

e.g. lines below would probably mimic your gsas fit:

lam ymin_on_ymax 0.0001
Lam_recs
{
0.5981 1.788960 1.0000
}

John

ben1980

Hi John,

Thanks very much.

Just a final question, can I refine the parameters in the emission profile apart from wavelength?

I tried to set 0.5981 and 1.0000 in { 0.5981 1.788960 1.0000 } as refineable parameters and i got far better

refined peaks. Not sure if i did things correct.

Cheers

Ben

johnsoevans

Ben,

My mistake. The first column is the relative proportion of each wavelength in emission profile. As you say, the first column can be 1.000. In fact this correlates 100% with scale so it doesn't matter. Apologies.

John