- Ifeffit - millenia.cars.aps.anl.gov

RE: Ifeffit Digest, Vol 34, Issue 18
by Vivek Srinivasamurthi 19 Dec '05

19 Dec '05

Shelly, Sorry, forgot to attach the file before.. vivek -----Original Message----- From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of ifeffit-request(a)millenia.cars.aps.anl.gov Sent: Monday, December 19, 2005 11:12 AM To: ifeffit(a)millenia.cars.aps.anl.gov Subject: Ifeffit Digest, Vol 34, Issue 18 Send Ifeffit mailing list submissions to ifeffit(a)millenia.cars.aps.anl.gov To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request(a)millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner(a)millenia.cars.aps.anl.gov When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Pd data (Kelly, Shelly D.) 2. RE: Pd data (Barton, David (DG)) ---------------------------------------------------------------------- Message: 1 Date: Mon, 19 Dec 2005 09:37:47 -0600 From: "Kelly, Shelly D." <SKelly(a)anl.gov> Subject: [Ifeffit] Pd data To: "XAFS Analysis using Ifeffit" <ifeffit(a)millenia.cars.aps.anl.gov> Message-ID: <A7B9B5614B54BE48B378DAE209FECC30ABE841(a)ROCKY.anl.gov> Content-Type: text/plain; charset="us-ascii" Hello friends, Does anyone have Pd foil data or know of an EXAFS study that models the data beyond the first shell? I have some data but it doesn't seem to correspond to the crystallographic structure of Pd. I'm suspicious that something about the foil sample caused the structure to become non-ideal. Thanks Shelly

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RE: Ifeffit Digest, Vol 34, Issue 18
by Vivek Srinivasamurthi 19 Dec '05

19 Dec '05

Shelly, Attached is a Pd nanoparticle sample on a carbon support. The data was taken upto 18 k-space. It also has a Pd foil in the reference channel. The data was collected with a Si(111) monochromator at BNL-NSLS -X18B. Vivek -----Original Message----- From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of ifeffit-request(a)millenia.cars.aps.anl.gov Sent: Monday, December 19, 2005 11:12 AM To: ifeffit(a)millenia.cars.aps.anl.gov Subject: Ifeffit Digest, Vol 34, Issue 18 Send Ifeffit mailing list submissions to ifeffit(a)millenia.cars.aps.anl.gov To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request(a)millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner(a)millenia.cars.aps.anl.gov When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Pd data (Kelly, Shelly D.) 2. RE: Pd data (Barton, David (DG)) ---------------------------------------------------------------------- Message: 1 Date: Mon, 19 Dec 2005 09:37:47 -0600 From: "Kelly, Shelly D." <SKelly(a)anl.gov> Subject: [Ifeffit] Pd data To: "XAFS Analysis using Ifeffit" <ifeffit(a)millenia.cars.aps.anl.gov> Message-ID: <A7B9B5614B54BE48B378DAE209FECC30ABE841(a)ROCKY.anl.gov> Content-Type: text/plain; charset="us-ascii" Hello friends, Does anyone have Pd foil data or know of an EXAFS study that models the data beyond the first shell? I have some data but it doesn't seem to correspond to the crystallographic structure of Pd. I'm suspicious that something about the foil sample caused the structure to become non-ideal. Thanks Shelly

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RE: [Ifeffit] Pd data
by Barton, David (DG) 19 Dec '05

19 Dec '05

Shelly, Attached is a Pd foil data set. It was only collected out to k=16A-1, otherwise the data looks great. Data was collected with Si111 mono at DND-CAT (APS-ANL). Dave -----Original Message----- From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Kelly, Shelly D. Sent: Monday, December 19, 2005 10:38 AM To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Pd data Hello friends, Does anyone have Pd foil data or know of an EXAFS study that models the data beyond the first shell? I have some data but it doesn't seem to correspond to the crystallographic structure of Pd. I'm suspicious that something about the foil sample caused the structure to become non-ideal. Thanks Shelly

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Pd data
by Kelly, Shelly D. 19 Dec '05

19 Dec '05

Hello friends, Does anyone have Pd foil data or know of an EXAFS study that models the data beyond the first shell? I have some data but it doesn't seem to correspond to the crystallographic structure of Pd. I'm suspicious that something about the foil sample caused the structure to become non-ideal. Thanks Shelly

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Re: [Ifeffit] Mac installer for 10.4 with horae-048
by Matt Newville 15 Dec '05

15 Dec '05

Stefano, Paul, I just tried this on a fairly fresh OS 10.4 machine (Ifeffit had been installed over a year ago, when it was a 10.3 machine, and I wiped /Library/Perl/5.8.1 and /Applications/Ifeffit, and cleared the /Library/Receipt for Ifeffit....). I got the same behaviour as Stefano. It looks like everything did get installed this time, but that the resulting version of Ifeffit depends on Aquaterm. Downloading and installing Aquaterm from the disk-image package from sourceforge.net was simple (though it requires a privileged password) and made Athena and Artemis run fine. So my immediate recommendation is to install Aquaterm from Sourceforge. http://sourceforge.net/projects/aquaterm/ --Matt PS: We should probably also figure out how to not depend on Aquaterm, but telling people they need Aquaterm as well as X11.app seems simple enough.

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IFEFFIT installation problem
by Frenkel, Anatoly 15 Dec '05

15 Dec '05

On behalf of Joe Woicik (please reply to: woicik(a)bnl.gov) I downloaded version 1.2.8. Runner. exe gives me the following error and Athena does not run. Please let me know if anyone on the list has experienced similar problem. Joe Woicik Traceback (most recent call last): File "runner.py", line 753, in ? File "runner.py", line 184, in __init__ File "runner.py", line 275, in LookForUpdates File "runner.py", line 299, in read_web_version File "urllib.pyc", line 76, in urlopen File "urllib.pyc", line 181, in open File "urllib.pyc", line 297, in open_http File "httplib.pyc", line 712, in endheaders File "httplib.pyc", line 597, in _send_output File "httplib.pyc", line 564, in send File "httplib.pyc", line 538, in connect File "timeoutsocket.pyc", line 237, in connect timeoutsocket.Timeout: Attempted connect to ('164.54.160.111', 80) timed out. Traceback (most recent call last): File "runner.py", line 753, in ? File "runner.py", line 184, in __init__ File "runner.py", line 275, in LookForUpdates File "runner.py", line 299, in read_web_version File "urllib.pyc", line 76, in urlopen File "urllib.pyc", line 181, in open File "urllib.pyc", line 297, in open_http File "httplib.pyc", line 712, in endheaders File "httplib.pyc", line 597, in _send_output File "httplib.pyc", line 564, in send File "httplib.pyc", line 538, in connect File "timeoutsocket.pyc", line 237, in connect timeoutsocket.Timeout: Attempted connect to ('164.54.160.111', 80) timed out. Traceback (most recent call last): File "runner.py", line 753, in ? File "runner.py", line 184, in __init__ File "runner.py", line 275, in LookForUpdates File "runner.py", line 299, in read_web_version File "urllib.pyc", line 76, in urlopen File "urllib.pyc", line 181, in open File "urllib.pyc", line 297, in open_http File "httplib.pyc", line 712, in endheaders File "httplib.pyc", line 597, in _send_output File "httplib.pyc", line 564, in send File "httplib.pyc", line 538, in connect File "timeoutsocket.pyc", line 237, in connect timeoutsocket.Timeout: Attempted connect to ('164.54.160.111', 80) timed out.

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RE: [Ifeffit] my problem
by Frenkel, Anatoly 15 Dec '05

15 Dec '05

You cannot resolve these sites from EXAFS analysis. Even if you had only 2 inequivalent sites of the same central atom with occupancies N1 and N2, you would not be able to resolve N1 and N2 in the fit because different Nb atoms would have similar environments (e.g., 4 and 6 oxygens), and they will have similar Nb-O distances around each site. The best you can do is to try to fit the first nearest neighbor peak as an average Nb-O contribution (if it is a well isolated peak) and try to make use of sigma2 that may turn out to be larger than in some well known Nb oxide reference that you should analyze first. Anatoly -----Original Message----- From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov]On Behalf Of Tadej Rojac Sent: Thursday, December 15, 2005 7:44 AM To: Ifeffit(a)millenia.cars.aps.anl.gov Subject: [Ifeffit] my problem Dear collegues, my name is Tadej Rojac and I'm writing from the Institute Jozef Stefan in Ljubljana, Slovenia. I work in the Department of electronic ceramics. Actually, I'm working on a EXAFS spectra with Artemis. What I am trying to do is mainly to describe an EXAFS spectrum with a model concerning the structure of Nb2O5. I'm working togheter with prof. Iztok Arcon, who is a specialist in the field. My main problem is that I have to do some suppositions. In fact Nb2O5 structure is quite complicated. It is composed of seven different Nb positions which I took into account using 7 feffs in Artemis. I don't know the exact occupancies of the seven positions. In order to make the search easier I did at first a supposition that all the occupancies must be positive, which is realistic. I set this with the command "abs" in each feff file. Secondly, I need to supose that the sum of all occupancies is 1. In that way the search for the result is much easier, otherwise I get the sum greater than one, which, for sure, is not the case. My question is how can I do that? For example, if the occupancies are O1, O2, O3, O4, O5, O6 and O7 and I define them with a starting value (let use say the same, so 1/7) than I can do O = O1+O2+O3+O4+O5+O6+O7. Finally I need to do O =1, but here Artemis doesn't want to define the same parameter (O in this case) twice. So, how can I insert the conditions, that the sum of all the occupancies is 1, into Artemis? I hope you can help me. I'm looking forward t hearing from you...thank you... Tadej Rojac Jozef Stefan Institute Jamova 39 1000 Ljubljana Slovenia Tel.: +386 1 477 38 34 Fax: +386 1 477 38 87 E-mail: tadej.rojac(a)ijs.si

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RE: [Ifeffit] my problem
by Kelly, Shelly D. 15 Dec '05

15 Dec '05

Hi Tadej, ________________________________ From: ifeffit-bounces(a)millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Tadej Rojac Sent: Thursday, December 15, 2005 6:44 AM To: Ifeffit(a)millenia.cars.aps.anl.gov Subject: [Ifeffit] my problem Dear collegues, my name is Tadej Rojac and I'm writing from the Institute Jozef Stefan in Ljubljana, Slovenia. I work in the Department of electronic ceramics. Actually, I'm working on a EXAFS spectra with Artemis. What I am trying to do is mainly to describe an EXAFS spectrum with a model concerning the structure of Nb2O5. I'm working togheter with prof. Iztok Arcon, who is a specialist in the field. My main problem is that I have to do some suppositions. In fact Nb2O5 structure is quite complicated. It is composed of seven different Nb positions which I took into account using 7 feffs in Artemis. I don't know the exact occupancies of the seven positions. In order to make the search easier I did at first a supposition that all the occupancies must be positive, which is realistic. I set this with the command "abs" in each feff file. Secondly, I need to supose that the sum of all occupancies is 1. In that way the search for the result is much easier, otherwise I get the sum greater than one, which, for sure, is not the case. My question is how can I do that? For example, if the occupancies are O1, O2, O3, O4, O5, O6 and O7 and I define them with a starting value (let use say the same, so 1/7) than I can do O = O1+O2+O3+O4+O5+O6+O7. Finally I need to do O =1, but here Artemis doesn't want to define the same parameter (O in this case) twice. So, how can I insert the conditions, that the sum of all the occupancies is 1, into Artemis? I hope you can help me. [Kelly, Shelly D.] In the path page for each path of each feff calculation you need to have a variable that represents the occupancy. S02xN = abs(S02 * O1) ..... Then in the variable page (guess set def) Guess O1 = 0.15 Guess O2 = 0.15 Guess O3 = 0.15 .... Def O7 = 1 - abs(O1) -abs(O2) -abs(O3) - abs(O4) - abs(O5) -abs(O6) Hence you get one occupancy for free for knowing one more piece of information. Sounds like a tough problem. I'm looking forward t hearing from you...thank you... Tadej Rojac Jozef Stefan Institute Jamova 39 1000 Ljubljana Slovenia Tel.: +386 1 477 38 34 Fax: +386 1 477 38 87 E-mail: tadej.rojac(a)ijs.si

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my problem
by Tadej Rojac 15 Dec '05

15 Dec '05

Dear collegues, my name is Tadej Rojac and I'm writing from the Institute Jozef Stefan in Ljubljana, Slovenia. I work in the Department of electronic ceramics. Actually, I'm working on a EXAFS spectra with Artemis. What I am trying to do is mainly to describe an EXAFS spectrum with a model concerning the structure of Nb2O5. I'm working togheter with prof. Iztok Arcon, who is a specialist in the field. My main problem is that I have to do some suppositions. In fact Nb2O5 structure is quite complicated. It is composed of seven different Nb positions which I took into account using 7 feffs in Artemis. I don't know the exact occupancies of the seven positions. In order to make the search easier I did at first a supposition that all the occupancies must be positive, which is realistic. I set this with the command "abs" in each feff file. Secondly, I need to supose that the sum of all occupancies is 1. In that way the search for the result is much easier, otherwise I get the sum greater than one, which, for sure, is not the case. My question is how can I do that? For example, if the occupancies are O1, O2, O3, O4, O5, O6 and O7 and I define them with a starting value (let use say the same, so 1/7) than I can do O = O1+O2+O3+O4+O5+O6+O7. Finally I need to do O =1, but here Artemis doesn't want to define the same parameter (O in this case) twice. So, how can I insert the conditions, that the sum of all the occupancies is 1, into Artemis? I hope you can help me. I'm looking forward t hearing from you...thank you... Tadej Rojac Jozef Stefan Institute Jamova 39 1000 Ljubljana Slovenia Tel.: +386 1 477 38 34 Fax: +386 1 477 38 87 E-mail: tadej.rojac(a)ijs.si

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Re: [Ifeffit] statistical parameters
by Matt Newville 15 Dec '05

15 Dec '05

Hi Stefano, all, > same old question that emerges again: > > What formula is used by IFEFFIT to calculate the number of > independent points? Does it use the formula 2DkDR/pi? or 2DkDR/pi +1? > or 2DkDR/pi +2? And how does it approximate the resulting number to > integer? Ifeffit uses an approximation of 2*delta_k * delta_R / pi. Well, it could use a better approximation -- see below. But Ifeffit does not use 2dKdR/pi + 2. The Stern paper considers "independent points" to be discrete, counts the endpoints of this discrete array of "independent points", and neglects the rather significant problem of the limit dk->0. I find each of these to be problematic. The dk->0 limit problem makes it especially hard to implement in a meaningful way. Ifeffit uses n_idp = 2*delta_k * delta_R / pi, but is cautious (and probably overly so) in determining delta_k and delta_R. First, it puts these on the k- and R- grids (0.05 Ang^-1 and ~0.03067Ang). It is also works to avoid rounding incorrectly. Thus, currently your ranges: kmin=2.0, kmax=12, rmin=1.0, rmax=6.0 get mapped to kmin = 2.05, kmax=12.00 , rmin=1.012427, rmax=5.98525 Thus you should have n_idp = 31.4824. You can confirm that with 'print n_idp' from the command line. It sounds like that's what you're getting. And yes, I do think that having "kmin=2.00" map to "kmin=2.05" for this part of the calculation is overly cautious, and I will fix that in the next release (and n_idp will equal ~31.64). I could be persuaded to just use the user-supplied values, but the round-off errors shouldn't matter much. In general, I agree with most of the answers to not take N_idp too seriously. I would say to report it to 1 decimal place, just to emphasize that it is understood to be an estimate and not a discrete number. Saying "n_idp=12" implies "I could fit up to 12 parameters with confidence". It's easy enough to show this is usually NOT the case, but some people sure like a hard and fast rule. And, sadly, n_idp does influence the error bars some, so it seems wise to get it as close as we can. That's sort of rambly, but hope that helps --Matt PS: For autobk/spline(), the number of knots is actually chosen as n = 2 * int( rbkg * (kmax-kmin)/pi ) + 1 It turns out that for the b-spline algorithm used, the number of knots used needs to be an odd number greater than 4. So, the formula is convenient. Is it right? Well, it seems to work pretty well. As fitting variables, the spline y-values are somewhat correlated, so you might argue that you could have a few more variables. That's easy enough to try with spline(data.chi, rbkg=1, nknots=17) In my experience, this rarely helps but it might be worth re-visiting.

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