Re: [Ifeffit] Problem with Hephaestus at Ca L-edges (Matthew Marcus)

OK, at least we've come to convergence about what 'edge jump' means in this context. Do you think the Elam value for (mu(+)-mu(-))_L3/(mu(+)-mu(-))_L2 is correct? mam On 9/24/2015 10:36 AM, Matt Newville wrote: Hi Matthew, On Thu, Sep 24, 2015 at 11:47 AM, Matthew Marc

Re: [Ifeffit] Problem with Hephaestus at Ca L-edges (Matthew Marcus)

OK. Now I get it. Why use 50eV? Since lifetime and other broadening is not taken into acocunt in any of these tables, why not use a very small number? mam On 9/24/2015 11:07 AM, Bruce Ravel wrote: On 09/24/2015 01:43 PM, Matthew Marcus wrote: See the attached ppt for the demo. I

Re: [Ifeffit] Unable to run Demeter on EPA computers

This is an application for an acronym: SIMWA! Security In My Way Again! mam On 10/22/2015 11:46 AM, Matt Noerpel wrote: Thank you for your time, Bruce. The IT person tried it with and without the AV running (Symantec) and neither worked. Additionally, the AV does run in Safe Mode. I

Re: [Ifeffit] CuO XAS spectrum

There are two spectra (transmission, probably) in the XAFS Model Compound Library http://cars9.uchicago.edu/cgi-bin/newville/Model-Search.cgi . mam On 12/2/2015 3:32 PM, Enyuan Hu wrote: Dear all, I'm analyzing some Cu compounds spectra and was wondering if anyone has the CuO XAS spec

Re: [Ifeffit] Ifeffit Digest, Vol 156, Issue 4

I have an SDD and find very little strength in the escape peak or the Si Ka peak. I have seen Si from the sample. I can't speak to how well Si XAS works because my beamline doesn't go down that far. mam On 2/9/2016 10:25 AM, Pierre Lecante wrote: Hi Pinit, here is what you can expec

Re: [Ifeffit] Ifeffit Digest, Vol 158, Issue 3

It shouldn't be called 'self-absorption'. That's a misnomer, which seems to have come from a 1992 paper (Troger, et. al."Full correction of the self-absorption in soft-fluorescence extended x-ray-absorption fine structure", PRB 46,3283 (1992). The effect was described and analyzed in a 1982 pa

Re: [Ifeffit] Ifeffit Digest, Vol 158, Issue 3

nown parameter. Still, I wouldn't necessarily trust Debye-Waller (ss2) values taken from EXAFS on strongly overabsorbed samples, even with a correction that gets the right coordination number. mam On 4/3/2016 7:04 PM, Matt Newville wrote: Hi Matthew, On Sun, Apr 3, 2016 at 8:13 P

[Ifeffit] Other programs than FEFF - GNXAS and MXAN

I heard a talk by Ziyu Wu of Beijing Synchrotron Radiation Facility in which he said that the international community prefers a package called GNAXS to FEFF for EXAFS calculations. He also has his own package called MXAN for XANES fitting. What do other people think of these programs? Would it

Re: [Ifeffit] Other programs than FEFF - GNXAS and MXAN

One reason I can think of for GNXAS to be less popular than FEFF is that it hasn't been compiled for Windows. It exists only for various forms of Unix. The website says that it's fortran, so there's no reason I can see that it couldn't be compiled for Windows, depending on whether it needs som

Re: [Ifeffit] mxan and gnxas

Thanks. Do you mean that it's available as source-code only? Is there any tutorial material available? If it does background subtraction, does that mean you feed it raw signal-vs-energy files? mam - Original Message - From: "Francesco Giannici" <[EMAIL PROTECTED]> To: "ifeffit"

Re: [Ifeffit] Other programs than FEFF - GNXAS and MXAN

Feff deliberately did not include graphics or analysis, with the hope / expectation that lots of other people would do this. This turned out to be true, and very many analysis programs use Feff. It is perhaps interesting that this has not happened for GNXAS. In contrast, it is uninteresting fo

Re: [Ifeffit] Other programs than FEFF - GNXAS and MXAN

Including only bare-bones ASCII in/out is, IMHO, the only way to obtain true portability, and it has worked. I vaguely recall that they use some sort of verifier on their code to screen out system dependencies. I don't understand this. A verifier is a program that inspects programs, lookin

Re: [Ifeffit] Re: XAFS Analysis using Ifeffit

How do you get those absorption backgrounds, free of EXAFS? I can see it for Kr, but how did you do it for the other, chemically-reactive elements? mam - Original Message - From: "Alojz Kodre" <[EMAIL PROTECTED]> To: "Matt Newville" <[EMAIL PROTECTED]>; "XAFS Analysis using Ifeffit"

[Ifeffit] Attempted XANES calc using FEFF8.1 - what's wrong?

I tried the XANES calculation on FEFF8.10 with calcite at the Ca K-edge as the object. I had just taken some data on this compound, and I wanted to see how it compares. The attached shows that it doesn't compare all that well. I've also attached the feff.inp file I used, which was made by ATOM

Re: [Ifeffit] Attempted XANES calc using FEFF8.1 - what's wrong?

With all the playing around one has to do to get a known structure to agree, how can one fit unknown structures? What started this whole thread was the talk I heard by Wu Ziyu who claimed to fit metalloprotein structures based on subtle features of the XANES, while I can't even get the broad fe

Re: [Ifeffit] Attempted XANES calc using FEFF8.1 - what's wrong?

This all suggests that Ziyi Wu's claims to be able to tell the difference between 4 and 5 waters of hydration in the metal center of a protein just from fitting XANES features may be a bit overblown. I tried again with FEFF8 and still don't see the pre-edge features, nor get the ratios right.

Re: [Ifeffit] Phase corrected Fourier transforms

OK, I have to put in my US$0.02/e0.02. The phase correction can't mean much if the scattering atoms are different, which is usually the case. If the scattering atoms are very heavy, then the phase correction has a kink in it which could cause strange shapes if applied to light-atom shells. I'v

[Ifeffit] Filter window shape for FT?

I've always been told that when doing Fourier filtering, the R-space window shouldn't have sharp corners. Artemis, for instance, allows you to vary this, and by default puts shoulders on the window. I have a user who now wants the sharp corners, claiming that it provides the best filtering. H

Re: [Ifeffit] Filter window shape for FT?

This is about going to what you guys call q-space. It's often of interest to be able to display the contributions from specific shells, thus showing off such things as beat-nodes. For instance, in phyllomanganates, the Mn-O first shell is often not of great interest, but the split Mn-Mn second

Re: [Ifeffit] Re: Novice FEFF question--feel free to post

As usual, consistency is everything. It seems to me that one should always compare with a model compound, if possible. If you do that and do the model and unknown the same way, then you need only take the ratios of S0^2 or N or whatever. mam - Original Message - From: "Bruce Ravel"

Re: [Ifeffit] CN and bond distances in Artemis

I imagine somebody has done so and would be willing to provide that data. Unfortunately, the Newville database doesn't have it, and I don't think I do. Anatoly, surely you must have done Pt foil? Yes, I know it's best to measure everything on the same beamline, but it's not essential. mam

Re: [Ifeffit] 2007 NSLS XAFS workshop: save the date

This sounds possibly interesting. I wonder if experience with my own code would suffice instead of experience with Athena, which I never did really learn. Anyway, I looked at yu.edu/scc and found no courses listed there newer than 2006. On another topic, do you know of a good book or review on

Re: [Ifeffit] 2007 NSLS XAFS workshop: save the date

That's great. Even though it will be several years, I'll still want to see the result when it happens. What you describe is exactly what I think is needed. mam - Original Message - From: "Scott Calvin" <[EMAIL PROTECTED]> To: "XAFS Analysis using Ifeffit" Sent: Wednesday, May 09, 2

Re: [Ifeffit] convergence of XANES for STO

How did you pick the values of the various parameters in the feff.inp file such as Vr, Vi and the SCF parameters? I once tried to do the Zn edge of ZnO and didn't come close, then gave up because there were too many parameters to play with. mam - Original Message - From: "Lena Fittin

Re: [Ifeffit] EXAFS Divination Dataset

Our library doesn't carry that journal. Could someone send me a copy or put it on an FTP site for download? Thanks. mam - Original Message - From: "Scott Calvin" <[EMAIL PROTECTED]> To: "XAFS Analysis using Ifeffit" Sent: Monday, June 25, 2007 4:40 AM Subject: Re: [Ifeffit] EXAFS D

Re: [Ifeffit] Artemis fitting using FEFF paths plusexperimentalreferences

The particles are ~8nm diameter, and the distances involved are 0.3-0.34nm, so that's only a 6% effect. Also, the fitted Fe-Fe coordinations vary with oxidation temperature, with the biggest deficits at the lowest temps. The particles actually hollow more at the higher temperature, so one would

Re: [Ifeffit] help: can I use ifeffit to predict chi?

I have sent Chen some data on magnetite and maghemite. mam - Original Message - From: "Tai-Yen Chen" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "XAFS Analysis using Ifeffit" Sent: Friday, November 02, 2007 10:53 AM Subject: Re: [Ifeffit] help: can I use ifeffit to predict chi? >

Re: [Ifeffit] Self absorption questions

You can find a writeup which explains overabsorption in great and gory detail at http://xraysweb.lbl.gov/uxas/Beamline/Operation/Operation.htm . mam - Original Message - From: "Richard Mayes" <[EMAIL PROTECTED]> To: "XAFS Analysis using Ifeffit" Sent: Wednesday, November 07, 2007 7:39

Re: [Ifeffit] Self absorption questions

er one: A. I. Frenkel, D. M. Pease, J. I. Budnick, P. Shanthakumar, T. Huang Application of Glancing Emergent Angle Flourescence for Polarized XAFS Studies of Single Crystals J. Synchrotron Rad. 14, 272-275 (2007) Anatoly -Original Message- From: [EMAIL PROTECTED]

Re: [Ifeffit] GaN atoms imput page

If you know the positional parameter (the 0.375) and the lattice parameters, you can pull up the input file for any other wurzite structure and modify to suit. That's probably the easiest way. mam - Original Message - From: "Bruce Ravel" <[EMAIL PROTECTED]> To: "XAFS Analysis using

Re: [Ifeffit] Artemis

Did you check the data range and interpolation as I suggested? mam - Original Message - From: "Alain Manceau" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: Sent: Thursday, January 10, 2008 3:30 AM Subject: Re: [Ifeffit] Artemis > Bruce, > >>I just tried artemis with feff7 and it

[Ifeffit] switching to FEFF8 in Artemis

I have FEFF8 and would like to get Artemis to use it for EXAFS calculations. I figured out how to use the Edit Preferences menu to point Artemis to the executable and how to get the ATOMS module to use the FEFF8_EXAFS template to generate feff.inp files which result in the generation of feffNNN

Re: [Ifeffit] switching to FEFF8 in Artemis

> > Is "QFS" the quick fist shell theory thingie in the Theory menu? You > are correct -- it does not give you a choice. Using feff6 is > hardwired into it. It seems silly to me to use feff8 for the quick > first shell thing, but for the sake of completeness, it should be > fixed. Yes, it's the

Re: [Ifeffit] Brainteaser

MessageThe most obvious explanation for why the post-edge scans line up and the pre-edges don't is that the transmission chamber current amp or V/F is saturated and reads a fixed value below the edge. As the ring current decays, I0 goes down while It is fixed below the edge, so ln(I0/It) decreas

Re: [Ifeffit] Cumulant expansion fittings

OK, here's my alternative for modeling asymmetric distributions: I use for the effective RDF a Gaussian-broadened exponential tail function. The tail function is defined as: t(r) = (1/|w|)*exp(-r/w) r*sign(w) >0 0 r*sign(w) <= 0 This limits to a delta function for w->0.

Re: [Ifeffit] (no subject)

Wback in the 70s and 80s, Powers, et. al. claimed to observe a Cu-Fe distance of 3.75A, seeing it in both the Cu and Fe edges. However, a bit of Googling shows that this result is in some doubt. I once saw a Cr-Cr distance of 6 or 7A in a Cr-bis(arene) complex at 8K. Sometimes, the contributi

[Ifeffit] ISO Calcite + dolomite EXAFS

Does anyone have Ca K-edge EXAFS data they can share for calcite and dolomite? I took some, but it seems to disagree with FEFF as to the position of the Ca-(Ca,Mg) peak. mam ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://mill

Re: [Ifeffit] ISO Calcite + dolomite EXAFS

5:31 PM, Matthew Marcus wrote: Does anyone have Ca K-edge EXAFS data they can share for calcite and dolomite? I took some, but it seems to disagree with FEFF as to the position of the Ca-(Ca,Mg) peak. mam ___ Ifeffit mailing list If

Re: [Ifeffit] No Reference Foil

Just a caveat - CeO2 and Ce(OH)4 have XANES which isn't quite the same as other Ce4+. There's a shoulder on the low side, as if it were slightly reduced, and the first peak is at a slightly different position. Of course, you can use LCF with CeO2 as one of the refs if you need to.

Re: [Ifeffit] No Reference Foil... Continued

I find that the main effect of the multi-electron excitations is to make a pair of bumps in an unfortunate region of the spectrum, which need to be subtracted out before EXAFS analysis can begin. The positions and amplitudes of these bumps are known for Ce3+ and Ce4+, so if you start with post

[Ifeffit] fitting of S XANES with arctans and gaussians

I'm trying to fit 37 micro-XANES spectra taken at the S K-edge, using the method discussed in the paper by Manceau and Nagy "Quantitative analysis of sulfur functional groups in natural organic matter by XANES spectroscopy", Geochimica et Cosmochimica Acta 99 (2012) 206–223. In this paper, the

Re: [Ifeffit] determining reasonable fitting parameters

Did you do any correction for the multi-electron bumps? Here's a note I made for myself when doing CeO2 EXAFS: Problem: Ce L3-edge spectra are polluted by multi-electron peaks (MEP) which appear as bumps right in the important range and can corrupt 1st-shell analysis, Gomilšek, et, al (Acta

Re: [Ifeffit] determining reasonable fitting parameters

The reference spectrum provided in Hepheastus only goes out 50eV above the edge. How can you do EXAFS analysis on that? Am I missing something? Here's an EXAFS-length CeO2 ref, pre-edge subtracted and post-edge normalized for your XANES'ing pleasure. mam On 7/27/2016 12:53 PM, Neil M

Re: [Ifeffit] determining reasonable fitting parameters

I'm not sure I get your point about ion-chamber response. Shouldn't that normalize out in post-edge spline? If the I0 chamber gets less sensitive as a function of energy, then the post-edge background rises by the same amount as the wiggles get bigger, so it divides out. Similarly for probe-de

Re: [Ifeffit] determining reasonable fitting parameters

vel wrote: On 07/27/2016 04:39 PM, Matthew Marcus wrote: I'm not sure I get your point about ion-chamber response. Shouldn't that normalize out in post-edge spline? Athena edge-step normalizes (i.e. normalizes by a constant) by default. It does not do a functional (or energy dependen

Re: [Ifeffit] determining reasonable fitting parameters

r the post-edge division. mam On 7/27/2016 2:08 PM, Bruce Ravel wrote: On 07/27/2016 04:56 PM, Matthew Marcus wrote: Oh, so it assumes that chi(k) = (mu(E(k))-spline(k))/const.? Mine does (mu(E(k))-spline(k))/spline(k), which I guess has its own problems Exactly. Both solutions hav

Re: [Ifeffit] Questions about fitting of EXAFS

This point may have come up before in this thread or in one of the numerous links, but I'd like to note that the FEFF version used by default in Artemis usually requires large E0 for heavy elements like Pt. Often, the E0 that results in small values of enot is at or above the white line. An ea

Re: [Ifeffit] Multi-electron peak in Yb

s not Fe either. mam On 8/4/2016 4:20 PM, Matt Newville wrote: Hi Matthew, On Thu, Aug 4, 2016 at 2:24 PM, Matthew Marcus mailto:mamar...@lbl.gov>> wrote: Does anyone know of data on multi-electron peaks at the Yb L3 edge? One of the users here was just running Yb and fin

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

I'm afraid a PDF file of that sort is useless for EXAFS work because it doesn't tell you where the atoms are. It only tells you the size of the unit cell, unless you use it to solve the crystal structure yourself, which I don't recommend :-) You need to search the literature for structures whi

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

That's a theoretical paper, so I don't know how reliable those numbers are. It will take Han some care with crystallography to translate the data into something usable by Atoms, i.e. a complete site list. I suggest starting with structures with the same code (e.g. D022) and filling in new par

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

Use ATOMS, which lets you define the structure by filling in a form, then save as an ATOMS .inp file. You don't need the .cif. I forget whether ATOMS can save as .cif. The crystallographic symmetry rules will duplicate the O atom for you. The CIF only shows symmetry-inequivqlent atoms.

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

There are two different input files which take the extension .inp. One is the feff.inp file, which is the input to FEFF and contains a list of coordinates (Cartesian, not crystallographic) of all atoms surrounding an absorpber atom out to a certain distance. ATOMS produces this. The other is

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

s by that name.) —Scott Calvin Sarah Lawrence College On Aug 9, 2016, at 12:40 PM, Matthew Marcus wrote: There are two different input files which take the extension .inp. One is the feff.inp file, which is the input to FEFF and contains a list of coordinates (Cartesian, not crystallographi

Re: [Ifeffit] Converting PDF files to CIF files for usage in Artemis

Oh, the Demeter menu. I was looking in Artemis itself. Thanks! mam On 8/9/2016 11:07 AM, Bruce Ravel wrote: On 08/09/2016 01:50 PM, Matthew Marcus wrote: This actually results in a bit of inconvenience - if you want to use ATOMS, you have to load some data into Artemis and pretend

Re: [Ifeffit] Ifeffit Digest, Vol 162, Issue 17

Topic 3: Incorrect dark current (offset) is just one of many ways that glitches can escape being normalized out, and one of the few you can correct in software. Others include but are not limited to 1. Any detection-system nonlinearity in I0 or detected channel (F or T). This includes d

Re: [Ifeffit] Peakfitting CeO2 data in Athena

Instead of doing a bunch of peak fitting, try LSQ. Use CeO2 (bulk or nanos) for one reference and some Ce(III) for the other. Consistency check: see that the Ce(III) fraction is consistent over some set of Ce(III) references. Ce(III) has an assymetric white line, so it doesn't really fit a sin

Re: [Ifeffit] Peakfitting CeO2 data in Athena

nanoparticles, which are about 2-5 nm in diameter. Is there a good Ce(IV) ref for nanos that are in this size range? On Wed, Dec 7, 2016 at 2:37 PM, Matthew Marcus mailto:mamar...@lbl.gov>> wrote: Instead of doing a bunch of peak fitting, try LSQ. Use CeO2 (bulk or nanos) for one

Re: [Ifeffit] Peakfitting CeO2 data in Athena

The usual justification for using gaussians for peaks, aside from "it works" is that there's inhomogeneous broadening over and above the lifetime. The usual justification for using an arctan for the step is exactly the opposite. Instrument broadening is often taken to be gaussian. Net result: A

Re: [Ifeffit] Ifeffit Digest, Vol 170, Issue 19

Does Athena use a histogramming method for Fourier filtering? That's what I use. The idea is that to grid the data we don't interpolate but take averages over the data appearing within the bin, with interpolation only when there aren't any points within a bin. For those, you have to bridge a

Re: [Ifeffit] Ifeffit Digest, Vol 170, Issue 21

Date: Thu, 20 Apr 2017 22:33:14 -0500 From: Matt Newville To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Fwd: Ifeffit Digest, Vol 170, Issue 19 Message-ID: Content-Type: text/plain; charset="utf-8" Hi Matthew, On Thu, Apr 20, 2017 at 5:34 PM, Matthew Marcus wrote: Does

Re: [Ifeffit] E0 on linear combination fitting: fit or not?

My experience on ALS 10.3.2 is that shifts of up to about 0.5eV are plausible and often improve the fit substantially. I assume you're talking XANES, not EXAFS. 6eV is right out and suggests either a misidentification of the species (false fit) or inconsistency of energy cal. One of my pet p

Re: [Ifeffit] XAFS short course in BNL: Nov 1-3, 2017

x27;ll be able to go. It does sound interesting. My knowledge of XAS analysis has remained pretty static. Will there be anything that applies to soft X-rays? I'm moving to STXM, so will be dealing with soft X-rays. Sincerely, Matthew Marcus Dear subscribers: Please share with you

[Ifeffit] current-amp recommendation

I've gotten involved with a project in which stabilization of the position of a monochromatic, soft X-ray beam is needed. The offending frequencies seem to be vibration frequencies like 57 and 116Hz. We have in mind to use a thin Au film with a gap in the middle, measuring the drain current fr

Re: [Ifeffit] EXAFS above 5 angstroms

erify that these two approaches give you the same criterion for the visibility of a distant shell. This effect is indeed significant for heavy elements, either at the L-edge (5d and actinides) or K-edge (4d and up). Sincerely, Matthew Marcus Daniel, Those distances are really far away

Re: [Ifeffit] Interpreting old XANES data with missing standards

ate glass would have sulfide in it? I'd think that it would have mostly sulfate and maybe sulfite. Check the peak position; it's a pretty reliable indicator of sulfite vs. sulfate vs. other. Here are some spectra taken in TEY mode with the calibration gypsum = 2482.75eV. Sincerely

Re: [Ifeffit] Bump/oscillating pattern at high energies of EXAFS

Agreed. The low frequency and high amplitude at the end is implausible as EXAFS. Sincerely, Matthew Marcus It is an effect of inhomogeneity of the sample, that is, the variation in the metal density throughout the X-ray beam footprint. Anatoly On Thu, Nov 1, 2018 at 5:34 PM Raj kumar

Re: [Ifeffit] EXAFS of solid-solution alloy

ences to the experimental data from each edge. Sincerely, Matthew Marcus Hi all, I have some problems in analyzing the EXAFS of solid-solution alloy, let us define as A0.5B0.5. I have searched the mailbox but cannot find similar discussion yet. So I post the question here and hope to get

Re: [Ifeffit] Two analysts, one spectrum, similar outcome?

#x27;, or 'Which of three structures does this most resemble?'. I love the idea of blind analysis comparison. Sincerely, Matthew Marcus The answer you get will depend somewhat on the assumptions you make.  if you are truly provided with data and no other information about the sample

[Ifeffit] Anyone use OCEAN?

if this might be a good forum for getting advice on solving problems with this code. Unlike ABINIT, which is one of the ab-inito engines OCEAN can use, OCEAN doesn't have a forum of its own. -- Sincerely, Matthew Marcus ___ Ifeffit mailing

Re: [Ifeffit] selection of pixels by criteria

A suggestion: Make a scatterplot available, plotting the pixel-by-pixel values of any two relevant quantities, and make it possible to define a polygon mask on that scatterplot. That often allows separation of chemically-distinct areas. Sincerely, Matthew Marcus On 11/21/2019 12:26 PM

[Ifeffit] what happened to the website?

The http://millenia.cars.aps.anl.gov/ website seems to have gone off-line, which means that WebAtoms doesn't work anymore. Is there a replacement? Of course, I can use the stand-alone Atoms in Demeter. -- Sincerely, Matthew Marcus ___ If

Re: [Ifeffit] what happened to the website?

oms. WebAtoms had a problem anyway - it wouldn't reliably handle more than 50 inequivalent sites. There are complicated mineral structures of low symmetry that easily blow past that. Sincerely, Matthew Marcus On 1/29/2020 3:09 PM, Jo Melville wrote: If you already have Demeter installed, it

Re: [Ifeffit] what happened to the website?

OK, thanks. I figured that you removed it because it's obsolete. Are you sure the server isn't running Windows 7? :-) Sincerely, Matthew Marcus On 1/29/2020 3:48 PM, Matt Newville wrote: Hi Matthew, On Wed, Jan 29, 2020 at 4:39 PM Matthew Marcus mailto:mamar...@lbl.g

Re: [Ifeffit] errors in bond lengths

The uncertainties reported by Artemis include as 'noise' the systematic deviation of FEFF calculation from the real thing. Even if FEFF were perfect, those FEFF calcs haven't been through the mutilations inflicted by data reduction, such as spline fitting. What I've done when looking at close

Re: [Ifeffit] errors in bond lengths

Something I've done for analyzing DWF on data taken at several temperatures is what I called 'consensus amplitude' fitting. Here, I fitted shells to k^n*chi[i](k) = exp(-2 dsig2[i] k^2) A(k) sin(phi(k)+2 dr[i]k) where i is the index to temperature, and the fit parameters are A(k), phi(k), dr[

Re: [Ifeffit] Reported W L3-edge and L2-edge energy

This paper: Kraft, S., Stümpel, J., Becker, P., & Kuetgens, U. (1996). High resolution x‐ray absorption spectroscopy with absolute energy calibration for the determination of absorption edge energies. Review of Scientific Instruments, 67(3), 681-687. has precision measurements of a bunch of e

Re: [Ifeffit] Reported W L3-edge and L2-edge energy

n air-bearing, I believe the angular accuracy and repeatability are very good.  I believe there are equally good moons in existence.   As Matthew Marcus pointed to the Kraft paper (which used an older source but 4-bounce mono to improve resolution), we find that Fe foil is definitely 

Re: [Ifeffit] [Ext] Re: XAS question

It's possible that your data really has a kink in it. Zoom in on that last bit in E space before any background subtraction and see if there's something odd-looking. If there's really an artifactual kink, then there's not much you can do. mam On 10/29/2020 7:47 AM, Carlo Segre wrote:

Re: [Ifeffit] [Ext] Analyzing EXAFS data on Artemis

If you go beyond first shell, then you'll need to take into account the Se-Se paths in Li2Se. That may be your best way of detecting Li2Se. mam On 5/27/2021 12:03 PM, Carlo Segre wrote: Hi Deltsidis: Using Artemis, you can compare the calculated Fourier Transforms of the Se-Fe and Se

Re: [Ifeffit] [Ext] Farrel Lytle database

As I recall, not only is the FL Dbase not in a standard format, but the format varies according to the vintage of the files. Also, there's no documentation except for the 1-line comment. mam On 7/6/2021 9:11 AM, Carlo Segre wrote: Dear Monica: The Lytle database is not in a current s

Re: [Ifeffit] Manuscript comments regarding EXAFS modeling

Was there a standard measured that's chemically similar to the unknown? If so, S0^2 could be set by requiring that the CN of the standard be what it's known to be. Often, the dσ² is mostly relevant in terms of differences or changes so an error in the absolute value isn't very important. If

Re: [Ifeffit] EXAFS Fitting with 2 CIF files

Extending what Scott said, I find it useful to make the coefficients abs(fracoxide) and abs(1-abs(fracoxide)) to avoid false minima with negative S0^2. mam On 9/4/2021 1:21 PM, Scott Calvin wrote: Hi Zihao, Do it by folding the molar ratio in to the amp parameter for each CIF. Of cou

Re: [Ifeffit] IFEFFIT file saving issue

This may sound like an 'is it plugged in?' sort of suggestion, but I wonder if there's a permissions issue. Perhaps IFEFFIT doesn't have write permission where it's trying to write. It might help people diagnose the problem if you were to specify the OS being used. mam On 9/7/2021 3

Re: [Ifeffit] IFEFFIT file saving issue

Or maybe save onto a USB drive. mam On 9/7/2021 3:58 PM, Matt Newville wrote: Hi Shinhyo, Liane, On Tue, Sep 7, 2021 at 5:39 PM Bang, Shinhyo > wrote: Thank you for the response. The OS is Windows 10. In addition to the symptom that was describ

Re: [Ifeffit] IFEFFIT file saving issue

There are other characters that Windoze doesn't like in filenames: |\/*":<>? mam On 9/7/2021 3:58 PM, Matt Newville wrote: Hi Shinhyo, Liane, On Tue, Sep 7, 2021 at 5:39 PM Bang, Shinhyo > wrote: Thank you for the response. The OS is Windows 10.

Re: [Ifeffit] IFEFFIT file saving issue

to a usb, and it WORKed! Thank you so much for your help. Best, Shinhyo -------- *보낸 사람:* Matthew Marcus mailto:mamar...@lbl.gov>> 대신 Ifeffit mailto:ifeffit-boun...@millenia.cars.aps.anl.gov>> *보낸 날짜:* 2021년 9월 7일 화요일 오후 4:11 *받는 사람:* ifeffit@millenia.cars.aps.anl.gov &

Re: [Ifeffit] S02 selection from reviewer

Since S02 is a parameter in the description of EXAFS and not of the experiment, it's independent of technique. Overabsorption (misnamed 'self-absorption') can reduce the *measured* amplitude, an effect which can be fudged in analysis by reducing S02. If the sample is truly homogeneous (on the

Re: [Ifeffit] Brain teaser

One thing that's pretty odd is that the glitches are peaks in I0, and dips in It. It would be much easier to explain if It was the one that increased steeply and I0 was more linear, but the presence of the edge in It shows that you didn't switch them. Red = It. What's that sudden drop at the

Re: [Ifeffit] Brain teaser

34 PM, matthew marcus wrote: One thing that's pretty odd is that the glitches are peaks in I0, and dips in It. It would be much easier to explain if It was the one that increased steeply and I0 was more linear, but the presence of the edge in It shows that you didn't switch them. Re

Re: [Ifeffit] [Ext] Brain teaser

The mirror was set up for a run at the Pd K-edge, according to the problem statement. Therefore, its nominal angle must be such as to put the critical energy >25keV. An angle of 3mrad would do it. At that angle, the reflectivity (assuming no roughness) goes up with energy in the relevant ran

Re: [Ifeffit] P K-edge EXAFS

It's not impossible, but difficult for a couple of reasons: 1. Not too many beamlines can do it. It's hard for soft X-ray beamlines and soft for hard X-ray beamlines. Air absorption is significant. If a Si DCM is used, the Bragg angle has to be higher than many monochromators can reach. 2.

Re: [Ifeffit] P K-edge EXAFS

Good points. At these low energies, an EXAFS range is a large fraction of the total energy range, so there tends to be a lot of curvature of baselines and post-edges. True about the 4O 1NN shell that dominates, but the same happens with As. All the interesting stuff is in the higher shells.

Re: [Ifeffit] test/validation sample for air-sensitive sample cells?

to Fe3+. Sincerely, Matthew Marcus On 2/21/2024 10:44 AM, Gerald T. Seidler wrote: > Dear XAFS community, We've been developing air-sensitive sample cells for several of our XAFS experiments, but we don't have a good way of characterizing how well they actually reject air and

[Ifeffit] Modeling a spinel structure with fractional occupancy

A colleague want to fit EXAFS on a NiAl2O4-based material (I don't have the details). As shown in the attached CIF, Ni (the central atom) is distributed 60-40 between the 1 and 2 sites, and Al 20-80. I imagine that to model this, I'll need ZjQcmQRYFpfptBannerStart This

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