Dear all, I would like to go beyond the fitting of the first shell for a cobalt metallic foil acquired at FAME beamlime (ESRF). It's not mandatory for the determination of So in this case, but I just would like to improve myself in EXAFS fitting. The cobalt foil has an hexagonal structure (P 63/mmc, a =b=2.507 A, c= 4.068 A) according to the supplier. The first 49 scattering paths calculated with FEFF were selected to cover the R range up to 5.1 A. This include multiple scattering paths. The parametrization of those scattering paths is as follow (.apj enclosed) : - Distances : 1) a spherical expansion term was used to describe distance variation in [hkl] direction (reff*alpha1) with l considered as "large" when compared to h,k (reff*alpha1) 2) another spherical expansion term was used to describe distance variation in pure [hk0] direction (reff*alpha2) 3) a rough average of two previous expansion terms for [hkl] direction when h,k are comparable to l (reff*(alpha2+alpha1)/2). - For modeling disorder, the correlated Debye model was used with 3 parameters dt, dt2, dt3 (t =293K): 1) [hkl] direction with l considered as "large" : debye(t,dt) 2) pure [hk0] direction: debye(t,dt2) 3) for [hkl] direction with h,k comparable to l : debye(t,(dt+dt2)/2) But does this choice of parametrization is really reasonable? It seems very rough to me but when I look at the fit results it looks ok. - Uncertainty on : 1) Distances : is it simply delta(r) = reff*delta(alpha) ? 2) Debye-Waller : I can't figure out how to relate the uncertainty computed for the Debye temperatures (dt, dt2) to the uncertainties of the debye-waller terms for each scattering paths. Although I spent some times trying to understand this paper, http://journals.aps.org/prb/pdf/10.1103/PhysRevB.20.4908, I can't write a simple relation at the end. Many thanks for your kind help, Best Regards, Samy Ould-Chikh KAUST Catalysis Center Bldg.3,Level 4, #4231 4700 King Abdullah University of Science & Technology Thuwal 23955-6900 Kingdom of Saudi Arabia Tel: +966 12 8084486 E-mail: samy.ouldchikh@kaust.edu.sa Website: http://kcc.kaust.edu.sa/Pages/Home.aspx ________________________________ This message and its contents including attachments are intended solely for the original recipient. If you are not the intended recipient or have received this message in error, please notify me immediately and delete this message from your computer system. Any unauthorized use or distribution is prohibited. Please consider the environment before printing this email.