[RMCProfile-users] How much the value of "reduction factor" should be ? 1.0 ? or less than 0.1 ?

[Krayzman, Victor (Assoc)]

1.	A usual value of the reduction factor is about 0.9. You can set it to 0.9 for the beginning without a risk to make a big mistake.

2.	The reduction factor as it is assumed in EXAFS theory allows taking into account two things: 
        a)	So called the non-orthogonality of initial and final state atomic orbitals of the absorbing atom. 
        b)	Some defects of the sample such as the pinholes and/or  inhomogeneity of the sample thickness.

3.	FEFF can calculate the contribution to the reduction factor caused by the non-orthogonality of initial and final state atomic orbitals theoretically or it can accept the value provided by the user. If the FEFF user sets the amplitude reduction parameter >0.1 FEFF accepts this value, if the FEFF user sets the amplitude reduction parameter <0.1 FEFF understands that it must calculate this value. You can find the line e.g. like
#    S02=0.936
In the chi.dat file elaborated by FEFF.

4.	FEFF cannot calculate theoretically the contribution to the reduction factor caused by the sample defects. But this value can be estimated by the preliminary fit. Let’s assume you know the coordination number for the nearest neighbors N1 and force FEFF to calculate and use a theoretical value of the SO2. If you more or less successfully fit the first coordination sphere with theoretical values of SO2 and N1 you sample is excellent and you may use just a theoretical value of S02 as a reduction factor. If the FEFF preliminary fit gives a number of nearest neighbors N2<N1 then you have the set the reduction factor to the value S02*N2/N1.

I hope it will help for the beginning.
I will be happy to assist you in future.

Victor Krayzman

-----Original Message-----
From: rmcprofile-users [mailto:rmcprofile-users-bounces at rmcprofile.org] On Behalf Of sajiki gou
Sent: Thursday, September 01, 2016 12:48 AM
To: rmcprofile-users at rmcprofile.org
Subject: [RMCProfile-users] How much the value of "reduction factor" should be ? 1.0 ? or less than 0.1 ?

DEAR RMCprofile group

I would like to calculate using EXAFS data. 
To do so, we must obtain the some Paths.
To get a path, we must Run EXAFS_INTER.exe.

How much the value of "reduction factor" should be ?

In manual_rmc6f_exafs, It is written as follows : 
“The “reduction factor” is the So2 parameter obtained in the preliminary fit.”

In feff file (made at feff6l), It may have been written as follows:
“HOLE 1   1.0   *  Nb K edge  (18986.0 eV), second number is S0^2”

As mensined above, reduction factor is 1.

But, in manual_rmc6f_exafs, It is written as follows too:

“Perform self-consistent FEFF calculations of the scattering paths in a separate folder for each cluster. 
In the FEFF input file, set the amplitude-reduction parameter So2 to a value less than 0.1 to let FEFF estimate this parameter from the atomic overlap integrals.
dentify scattering paths to be used in the fit;”

reduction factor is 1.0 ? or less than 0.1 ?
If reduction factor is less than 0.1, How much it is normaly?

Thank you for your attention.

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桟敷 剛
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