[RMCProfile-users] [EXTERNAL] Refinement of Uiso

[Zhang, Yuanpeng]

Hi Andy,

I am not sure I get your point, but actually we are not refining Uiso as parameter in RMCProfile, since RMC method itself is not a parameterized approach for fitting data.

Really what we are doing with RMC method is that we create a supercell (or as people call it as 'big-box') containing a lot of atoms. Then by adjusting atom positions explicitly and calculating the signal (total scattering, EXAFS, etc.) afterwards, we are going to determine whether or not to accept moves depending on whether or not the promoted moves make the agreement with experimental data better.

Then after we are satisfied with the fitting (i.e. the agreement with experimental data looks good to us, both visually and statistically), we can grab the atomic configuration that we obtained from the RMC fitting and calculate the atomic displacement parameters (by collapsing the supercell back into unit cell) using the tool 'thermal_ellipsoid' that comes together with RMCProfile package.

I hope this helps you a bit. But if any questions, please feel free to either post it here or get in touch with myself directly. 

Cheers
Yuanpeng

-- 
 
Dr. Yuanpeng Zhang
Computational Instrument Scientist
Spallation Neutron Source
 
Oak Ridge National Laboratory
1 bethel valley road, Oak Ridge, TN 37830, US
Mobile: +1(865)-335-4818
Email: zhangy3 at ornl.gov | Web: https://www.iris2020.net <https://www.iris2020.net/>

On 10/27/20, 8:52 AM, "rmcprofile-users on behalf of Chun Mann Chin via rmcprofile-users" <rmcprofile-users-bounces at shadow.nd.rl.ac.uk on behalf of rmcprofile-users at shadow.nd.rl.ac.uk> wrote:

    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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