Liliana,
GSAS will refine the value of the absorption coefficient for neutron TOF data quite
easily (I recall one message of yours mentioned that your data was of this "flavor").
Just turn on the flag. Your Uiso's should rise for all atoms making those for the
heavy atoms positive. The ABS value
>Sorry for the ambiguous information I gave previously. The data at
>room temperature were taken with a variable wavelength (TOF) whether
>at low temperature the data were recorded with constant wavelength.
>There is no magnetic contribution on the pattern. The negative thermal
>parameters are for
Liliana,
You can calculate the absorption coefficient for your CW neutron experiment. GSAS
wants mu*R/lambda. Find a table of "true" neutron absorption cross sections for your
elements & calculate mu from them in cm-1. R is the radius of your sample can in cm.
Divide by 2 to correct for packing
Wait! I have to mention - the "heaviness" of atoms (atomic number Z) is
important in x-ray diffraction, but is uncorrelated with the neutron
scattering factor for the nuclei. When you say heavy, do you mean the
highly scattering ones for neutrons, or the high-Z ones?
- Ku
Sorry for the ambiguous information I gave previously. The data at
room temperature were taken with a variable wavelength (TOF) whether
at low temperature the data were recorded with constant wavelength.
There is no magnetic contribution on the pattern. The negative thermal
parameters are for the h
As people pointed out, thermal factors are underestimated (even negative) if
absorption is not corrected for. If you type "absorption" (or absorbtion :-) into the
search field of the Rietveld archive http://www.mail-archive.com/[EMAIL PROTECTED]/
you will find an earlier discussion on this.
Al
If you type "absorption" (or absorbtion :-) into the search field of the
Rietveld archive http://www.mail-archive.com/[EMAIL PROTECTED]/ you will
find an earlier discussion on this.
And also ~60 emails with the "absor(p/b)tion" keyword in the old
Rietveld 1994-1998 archive : http://sdpd.univ-lem
Title: RE: Re: thermal parameters at low temperature
ï
Liliana,
OK,
they should vibrate less... but are they good neutron scatterers or poor?
If they are poorly scattering, the thermal factors won't be as
meaningful.
- Kurt
---Kurt LeinenweberDepar
-
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Thu 2/26/2004 2:59 PM
To: [EMAIL PROTECTED]
Cc:
Subject: RE: Re: thermal parameters at low temperature
Liliana,
GSAS will refine the value of the
> ... the path of
> setting the absorption correction.
>
In expedt (after choosing the file): L, O, A, C
In EXPGUI: input window is behind "Globally Edit Absorption" buttom in the
Histogram panel.
Best Regards,
Markus
--
Markus Valkeapää, [EMAIL PROTECTED]
Inorganic Chemistry, Göteborg Univer
Kurt,
I mean heavy in the atomic number.
Liliana
-Original Message-
From: Kurt Leinenweber [mailto:[EMAIL PROTECTED]
Sent: Thu 2/26/2004 2:21 PM
To: [EMAIL PROTECTED]
Cc:
Subject: RE: Re: thermal parameters at low temperature
-
From: Maxim V. Lobanov [mailto:[EMAIL PROTECTED]
Sent: Thu 2/26/2004 1:59 PM
To: [EMAIL PROTECTED]
Cc:
Subject: RE: Re: thermal parameters at low temperature
>Sorry for the ambiguous information I gave previously. The
data
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