Matthew Newville et al 2009 J. Phys.: Conf. Ser. 190 012023 doi:10.1088/1742-6596/190/1/012023
Matthew Newville1, Josh J Kas2 and John J Rehr2
Show affiliationsWhile theoretical standards such as those from FEFF have many advantages for EXAFS analysis, the quality of fit statistics and estimation of parameter uncertainties has always been somewhat problematic using them. Even though the calculations reproduce EXAFS features sufficiently well to give bond distances accurate to 0.01Å or so, fits to high-quality experimental spectra will have fit residuals far larger than the experimental uncertainties. One of the possible causes for this mis-fit is from approximations made in the phenomenological calculations of the inelastic losses, though this has been difficult to test conclusively in the past. Recent improvements in calculations of inelastic losses using a many-pole self-energy (MPSE) using a real-space calculation of the dielectric function have been shown to give significant improvements in XANES calculations. Here, we discuss the use of MPSE calculations for EXAFS analysis, and show that these calculations from FEFF8.5 can quantitatively improve fit quality for EXAFS, reducing mis-fits by a factor of 2 or more compared to FEFF6. This approach may also allow the semi-physical fit parameter S02 to be avoided. The implications for improving precision for EXAFS analysis and the nature of the remaining fit residual are discussed.
78.70.Dm X-ray absorption spectra
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
Issue 1 (2009)
Matthew Newville et al 2009 J. Phys.: Conf. Ser. 190 012023
Kevin O'Grady 2009 J. Phys. D: Appl. Phys. 42 220301
Dhananjay Thakur et al 2009 Nanotechnology 20 485601
Adel Hamdi 2009 Inverse Problems 25 115009
Gernot J Pauschenwein and Gerhard Kahl 2009 J. Phys.: Condens. Matter 21 474202
Amitava Moitra et al 2008 J. Phys. D: Appl. Phys. 41 185406
Roland Kjellander 2009 J. Phys.: Condens. Matter 21 424101
B Joseph et al 2009 J. Phys.: Condens. Matter 21 432201
Asghar Ramezani and Aria Alasty 2009 J. Phys. D: Appl. Phys. 42 225506
Meijuan Yu et al 2009 J. Phys.: Conf. Ser. 190 012060