Powder pattern recording conditions, phase recognition, use of specific databases

Welcome to this Course, we hope that it will be of great value and interest to you.

Each week you will have lectures to read, software to download, install and test, and finally you will get exercises to solve. The exercise corrections will be provided as soon as we get your solution propositions. And you will then receive the next instructions.

You may contact the teachers at any time by e-mail for help and discussion. If you need 2 weeks or more instead of one, in order to be able to follow the next course instructions, this should be feasible because the 12-weeks course duration is only a suggested minimum.

Best wishes,

Alain Jouanneaux
Yvon Laligant
Armel Le Bail

P.S. 1 - Before to begin, you may feel interested in the following texts about distance education : "Students’ frustrations with a Web-based Distance Education Course: A Taboo Topic in the Discourse", and also by the official alt.education.distance FAQ (Frequently Asked Questions).

P.S. 2 - Evaluation of the course and teachers may be done at teacherReviews.com (use preferable Internet Explorer for that).

Week 1

Powder pattern recording conditions, phase recognition, use of specific databases.

Recommendations before starting

If not already done :

Subscribe to the SDPD Mailing List.
Subscribe to the Rietveld Mailing List.
Become familiar with the sci.techniques.xtallography and bionet.xtallography Newsgroups and complain to the alt.education.distance one.

And do not hesitate to contribute to the discussions, or ask for help.

Subscribe in order to receive the IUCr CPD Newsletter.
Subscribe in order to receive the IUCr general Newsletter.
Put the IUCr Web site URL in your bookmarks, and visit regularly the What is New page.

If you think that your knowledge in Crystallography needs to be improved, visit the Educational Resources IUCr Web page. Then try to learn more from all of these tutorials.

All the above is free.

Have at hands the following books, if possible (they will be referred as B1, B2 etc). With paperback, some of them are quite affordable (B2, B4...), but some are expensive, unfortunately.

B1- Introduction to X-ray Powder Diffractometry
by Ron Jenkins and Robert L. Snyder
Volume 138 of Chemical Analysis, Ed. J.D. Winefordner
Wiley-Interscience, 1996.

B2 - Modern Powder Diffraction
Reviews in Mineralogy, Volume 20
D.L. Bish and J.E. Post, Editors
Mineralogical Society of America, 1989.

B3 - The Rietveld Method
IUCr Monographs on Crystallography - 5
R.A. Young, Editor
Oxford Science Publication, 1993.

B4 - Fundamentals of Crystallography
IUCr Texts on Crystallography -2
C. Giacovazzo, Editor
Oxford Science Publication, 1992.

B5 - X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials
H.P Klug and L.E. Alexander
Wiley-Interscience, 1974, 2nd edition.

B6- Defects and Microstructure Analysis by Diffraction
R.L. Snyder, J. Fiala and H.J. Bunge,
IUCr Monographs on Crystallography, Vol 10,
Oxford Science Publications, 1999.

AND LAST BUT NOT LEAST :

B7- Structure Determination from Powder Diffraction Data
W.I.F. David, K. Shankland, L.B. McCusker, and Ch Baerlocher,
IUCr Monographs on Crystallography, Vol 13,
Oxford Science Publications, 2002.

Lectures

Read deeply chapters 1 to chapter 2.1, included, of the SDPD tutorial. Another way is to access to the Kunming Workshop conference text (part 1) which has a slightly different presentation on the Web, and may be more up to date. The lecture presents some cases of phase recognition.

If you disagree with some statements, do not hesitate to discuss the points by email. After all, you may be right.

Have a look at the L.M.D. Cranswick Hints on Phase Identification Using Powder X-ray Diffraction.

Finally, see how the 30 participants to the Search/Match Round Robin 2002 have performed for the phase identification of 4 samples. You may well get the data and try by yourself.

You may also consider to look at the book chapters :

B1 : Chapters 1 to 12. OK, this is almost the whole book ! But you already probably possess a lot of the knowledge described in that book, and may skip some parts.

The conference "Trends in Structure Determination by Powder Diffractometry", will give you an overview on the SDPD subject. You may download the full paper corresponding to this conference (in MS Word 97 format, zipped). Another conference text may be useful : "Standard and special strategies in structure determination from powder data".

P.S. - Do not forget the SDPD Internet Course FAQ.

Software to download

Theoretically, you should already have at hands a Search-Match program (it was a requirement for applying to this course). If not, however, have a look at the CCP14 Web page on this subject.

It is essential to be able to convert powder data to any format that you may need at any time. With those converter softwares below, you will translate to your favourite format all the .raw or .uxd datafiles (Siemens/Bruker), or others, which will be distributed along the SDPD Internet Course.

Some software are for peak fitting, or more, but can open and save in various formats. Note that the Siemens/Bruker .raw file is binary and that the .uxd is ASCII. Many times you may have to arrange an ASCII powder diffraction datafile into a different form for an entry in some software. For instance, the strategy retained when a pattern made at a synchrotron facility has to be examined by the EVA (Socabim) software for an attempt of identification or estimation of peak positions is the following : X-Y data are read by the Dat2rit program below which will create an uncomplete .uxd file, to be completed by adding manually the rest of the stuff (wavelength and so on) at the beginning of the file (done by using the MS Wordpad text editor and a cut and paste from a complete .uxd file + some hands on modifications). Then the XCH software (Socabim) is used for translating this .uxd file into a .raw file that can be read by EVA. Not that simple, but this may be the kind of thing that you may have frequently to do in powder diffraction jobs. Being a programmer would help you to build simple softwares like Dat2rit (Fortran, open source) or to modify them for special purposes.

You may find more details on some of the conversion software at the CCP14 page on that topic.

Convert or Powder by Nita Dragoe.

WinFIT by Stefan Krumm.

ConvX by Mark Bowden.

PowderX by Cheng Dong.

Axrlec and Dat2rit by Armel Le Bail : translate some simple formats to .rit and may perform elementary actions on powder data. Distributed with Fortran sources.

Install and test these programs, then, select those you prefer. Most programs have manuals and even tutorials. The course will try to honestly show the diversity of possible software. Thus, you cannot expect to obtain help for all software listed along the SDPD Internet Course, because the teachers cannot be familiar with all of them. Asking for help for a given software should be adressed to its author, after a careful reading of the manual.

You may try to find out more software by yourself, they probably exist (give us some feedback).

Exercises

We do not expect from you here always an exact result, though this would be possible sometimes, but an estimation depending on the database completeness (ICDD-PDF). Anyway, a maximum of 10 lines should suffice for giving this estimation for each exercise below.

1 - Sample-1 was synthesized by reacting in air CrO₃ with La(CH₃COO)₃.9H₂O at 600°C. The powder pattern was recorded on a Bruker D8 diffractometer, CuKalpha (sample1.raw, sample1.uxd, to be translated in another format if your search/match software needs it, this being part of the exercice).

Try to propose an identification by using the JCPDS-ICDD PDF-2 database.

2 - Sample-2 is obtained by scraping a white deposit on an old pottery bottle containing vinegar. The powder pattern was recorded on a Siemens D500, CuKalpha (sample2.raw; sample2.uxd).

What could be this deposit ?

3 - A series of 4 samples was collected by a polar expedition of geologists at the Kerguelen islands.The powder patterns were recorded on a Siemens D500, CuKalpha (sample3.raw, sample3.uxd; sample4.raw, sample4.uxd; sample5.raw, sample5.uxd; sample6.raw, sample6.uxd).

Try to propose an identification for all of them.

Note : data are also available in Philips .rd and .udf files and in Rigaku .dat formats.

As soon as we receive your solutions to these exercises (this may be longer than one week, at your convenience, the course is asynchronous), we will send you our corrections as a zipped html (or text) attached file together with the next instructions.

The two next weeks will be reserved for indexing.
Good luck !