Dear Brian ( & all),
The more recent versions of PC-GSAS (beta versions) have a new formulation
for the cylindrical absorption function that allows the value of muR/lam to
be much larger than one. For TOF data it is essential to refine the
absorption coefficient because of the wavelength dependence. Omission of
the absorption in a Rietveld refinement will lead (usually) to poor atomic
thermal motion parameters.
Bob Von Dreele
At 05:36 PM 2/3/00 -0600, you wrote:
>Dear All,
>
>I am currently trying to study a sample of Ba2In2O5 (pellet form diameter =
>0.9 cm. Density = 6.00 g/cm3) on GPPD at IPNS. So I am dealing with a Time
>of Flight neutron powder diffraction data. I use GSAS as the refinement
>package.
>
>This is a highly absorbing sample and I understand the arguments for keeping
>mu*R < 1 when dealing with CW neutron diffraction experiments. I am not,
>however, familiar with the determination of sample absorption using a TOF
>instrument and at what "hard values" I should consider that the absorption
>is causing a real problem with the corresponding Rietveld refinement.
>
>Any help or input in this matter would be greatly appreciated.
>
>Brian Mitchell
>
>Dr. Brian J. Mitchell GRSC
>IPNS Argonne B360 E205
>9700 S. Cass Ave.
>Argonne 60439-4814 IL
>Tel- (630)-252-5346
>Fax-(630)-252-4163
>email- [EMAIL PROTECTED]
