Asking questions, soliciting help

An excellent resource exists for anyone stumbling over the details of XAS experimentation or analysis – the Ifeffit mailing list. This low-noise, high-quality mailing list is populated by many of the world's expert practitioners of XAS and it handles dozens of questions every month. It should be the first place you go when you have a question about the software or about any other topic in XAS.

DEMETER's author, Bruce Ravel (that's me!), reads the mailing list and frequently responds to questions. You should send questions to the mailing list and not to me directly. My typical response to an unsolicited email about the software is a polite request to ask the same question on the mailing list.

Using the mailing list is in your best interest. The list gives you access to a large number of experts and to the entire IFEFFIT community. When you send you question directly to me, you may find me on travel, in the middle of an experiment, or simply not in the mood to read and write email. When you send mail to the list, you are much more likely to get a useful answer from someone – and that someone is often me. In fact, you may spark a discussion in which your question will be hashed out in much more detail than you would see in a response from a single person.

Don't believe me? Here is a nice example of a question asked which prompted answers from several different people. Follow the links that say “next message” to read the various answers to the question. After an interesting and useful discussion, the person with the original question had this to say.

Here is a searchable archive of the IFEFFIT mailing list. You may find that someone else has already asked your question.

How to ask for help

If you are asking for help, I encourage you to ask specific questions rather than vague ones. For example,

I don't understand multiple k-weight fitting. What does it mean to
use more than one k-weight in a fit and why should I want to do so?

is a good question and is likely to get a detailed answer. On the other hand,

I have lots of data from the synchrotron on TiO2 doped with
dysprosium. Can someone send me an atoms input file and tell me how
to get coordination numbers?

is a vague, open-ended question that is unlikely to garner much of a response. We see lots of these vague, open-ended questions and the folks asking questions like that rarely get the answer they're looking for. Spend time thinking about how to ask the question with clarity, with conciseness, and with precision – that time spent will pay off.

Remember that the people who answer questions on the mailing list are volunteering their time and may not have much time to spend with you.

Most questions about the use of the software will benefit by including example data or a project file that demonstrates your question. It is much easier to answer a questions if the problem can be reproduced on one's own computer.

For more hints about how to ask good questions How To Ask Questions The Smart Way by Eric Raymond and Rick Moen is very useful. (Please note that neither Raymond nor Moen are associated in any way with DEMETER, LARCH, or IFEFFIT nor should they be contacted with questions about DEMETER, LARCH, or IFEFFIT.)

Other XAFS Resources on the Web

The community web site, http://xafs.org, provides a wealth of information, educational materials, links to other sites of interest to XAS practitioners, and other community tools. The tutorials page contains links to educational materials written by a number of the luminaries of the XAS community. The workshops page lists links to several workshops and schools from recent years. Many of those workshops post PDF or PowerPoint files for the lectures given at the workshop. Go ahead and poke around http://xafs.org – many of your questions will be answered.

In November 2011, the Diamond Light Source invited me to do an XAS training course. All of the lectures were recorded as was the computer desktop during all lectures and demonstrations. The Diamond technical staff did a great job editing this metrial into several hours of streaming video. These are excellent references for using and understanding the software. (Here is a hint for following the Microsoft Media Server (mms:) links on that page if you are using Linux and Firefox. Presumably, similar solutions exist for other browsers.)

These are good overviews of XAS:

  • S.D. Kelly, D. Hesterberg, and B. Ravel. Analysis of Soils and Minerals using X-ray Absorption Spectroscopy. In L.R. Drees and A.L. Ulery, editors, Methods of Soil Analysis - Part 5: Mineralogical Methods, chapter 14. American Society of Agronomy, 2008. doi:10.2136/sssabookser5.5.
  • Matthew Newville. Fundamentals of XAFS. Reviews in Mineralogy and Geochemistry, 78(1):33–74, 2014. doi:10.2138/rmg.2014.78.2.
  • B. Ravel and M. Newville. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. Journal of Synchrotron Radiation, 12(4):537–541, 2005. doi:10.1107/S0909049505012719.

Scott Calvin's book XAFS for Everyone is my favorite XAFS textbook.

Grant Bunker's book is also excellent, although geared a bit more towards the physics or chemistry grad student.

Ifeffit and Demeter software

You can clone the DEMETER source code at https://github.com/bruceravel/demeter. Links to an installer package for Windows are also at https://bruceravel.github.io/demeter, as is documentation for ATHENA, ARTEMIS, and HEPHAESTUS.

Slide decks for the lectures the I give at XAS training courses can be found at https://speakerdeck.com/bruceravel. Those are all under a Creative Commons license, so feel free to download, share, and use ant of the materials found there.

Feff

If your question pertains to FEFF – specifically in the area of using FEFF for XANES calculations – remember that I am but a minor contributor to FEFF and may not in a position to answer your question authoritatively. The PI of the FEFF project and his team all read the Ifeffit mailing list and often answer questions posted there.

The FEFF homepage is at http://feffproject.org/. The FEFF9 document: in wiki format.



DEMETER is copyright © 2009-2016 Bruce Ravel – This document is copyright © 2016 Bruce Ravel

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