Dear iffefit user,
I found on a paper (E.A.
Stern et al. /Physica B 208&209 (1995) 117 120) the definition
of R quality factor as:
R_factor ≡ < ∆chi(R space))> = √[ ∑ |chi_C(Ri)
– chi_E(Ri)|2 / ∑( chi_E(Ri))2] --à
formula 3
Where Chi(Ri) is a complex function (imaginary and
real part of the XAFS spectra in the R space), C concerns the calculated XAFS
spectrum, while E refers to the experimental XAFS spectrum.
In the case of a linear combination fitting on the k space
performed by ATHENA, the <∆chi> needs a correction. Is it correct to
write:
R_factor ≡ < ∆chi(k space))> = √[ ∑ (chi_C(ki)
– chi_E(ki))2 / ∑( chi_E(ki))2] ?
Where Chi_C(ki) = x1*chi1(k)+x2*chi2(k) : chi1
and chi2 are the EXAFS functions of the two reference samples used for the
linear combination procedure and x1, x2 (with 0<x1,x2<1 and x1+x2=1) are their
weight; Chi_E(k) is the EXAFS experimental function of the investigated sample.
Best regards
Sebastiano Cammelli