[RMCProfile-users] Refinement of Uiso

[Playford, Helen (STFC,RAL,ISIS)]

Hi Andy,

I know we've just been talking about this offline, but I wanted to respond here in case anyone else is wondering. 

RMCProfile doesn't take information on thermal displacement from the GSAS/Rietveld refinement. The initial (unrefined) RMC configuration should produce calculated Bragg peaks that are more intense than the data, as though all your thermal displacements were set to zero (which in effect they are, because the initial configuration has all the atoms on their ideal crystallographic sites).

During the RMCProfile refinement the atoms will move away from these ideal positions according to the Bragg (and other) data. If you take a refined supercell and collapse it back down onto the initial unit cell you should see "clouds" or clusters of atoms around each of the crystallographic sites - these are pretty much equivalent to thermal ellipsoids, except they are not constrained to be any particular shape.

I will take a look at the files you sent and get back to you off the list shortly.

Best wishes,
Helen

-----Original Message-----
From: rmcprofile-users <rmcprofile-users-bounces at shadow.nd.rl.ac.uk> On Behalf Of Chun Mann Chin via rmcprofile-users
Sent: 27 October 2020 11:22
To: rmcprofile-users at rmcprofile.org
Cc: Chun Mann Chin <c.chin at sheffield.ac.uk>
Subject: [RMCProfile-users] Refinement of Uiso

Dear all,

Just curious as a novice user of RMCProfile, I wonder if the Uiso will be refined during the simulations. If not, does that mean the fitting/model is dependent on the initial GSAS Rietveld refinement?

Best wishes,
Andy

--
Dr Andy Chin

Department of Materials Science and Engineering University of Sheffield Sir Robert Hadfield Building Mappin Street Sheffield S1 3JD
01142 225510
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