ICDD Technical Committee Minutes

APPROVED MINUTES
Electron Diffraction Subcommittee
March 29, 2000
ICDD Headquarters
Chairman - Raymond Goehner

1. The Meeting was called to order by Ray Goehner with 32 people in attendance.

2. The minutes of the previous meeting were approved.

3. In the year 2005, a Special Topical Meeting will be held jointly between the Denver X-ray Conference™ and MAS (the Microbeam Analysis Society). All parties are very pleased that, after more than a decade of wishful thinking, this joint meeting will finally come to fruition. The exact subject matter of the meeting will be chosen closer to the date of the meeting.

4. Jim Kaduk addressed the meeting giving some background to the present situation and charging the Electron Diffraction Subcommittee with tasks for the next few years:

Background

a) There is some money available for the work of the subcommittee.

b) ICDD has acquired the electron diffraction data base, so it may be used as we wish.

c) Electron diffraction is important and ICDD is very positive in its attitude to its future.

Tasks

a) The subcommittee should continue to help define the way the product evolves. There has already been a significant effect on the Relational Data Base (RDB) but the subcommittee should not be satisfied with what has already been done.

b) The subcommittee should address the question of strengthening the links between the traditional powder diffraction community and the users of electron diffraction techniques. How can the traditional powder community be educated to understand the usefulness of electron beam techniques?

5. John Faber and Gerhard Grosse provided up-to-date information regarding the status of the RDB.

  • In the RDB there will be provision for calculating simulated powder patterns on the fly. In general, it will be possible to use the data to simulate many other experiments, but for now it is limited to x-ray powder patterns.
  • Where there is more than one file for the "same" structure there will be a flag to designate preferred data so that some files may be ignored if desired. The flag P indicates a published structure while A indicates alternative (which is to be translated as "unnecessary duplicate"). The flag D means deleted.
  • For the files calculated from the ICSD data base, the structure factors will be given separately for reflections with the same d-spacing. (The archetypical example is 333 and 511 in cubic systems.) [It was not mentioned at the meeting but another concern of electron diffraction has been addressed in these entries. Experimental x-ray data does not include large d spacings (which are needed for electron diffraction), but they have been included in these calculated files.]
  • Since last year there has not been progress in the direction of a joint data base to include both ICSD and PDF data but there has been progress in making them work together. A calculated PDF file in the RDB will include a reference to the ICSD file from which it was calculated. A reference in the reverse direction will come soon.

6. Ray Goehner made a brief report on the mid-year meeting of the Subcommittee which was held in Portland in conjunction with the M and M microscopy meeting.

7. It was decided to hold a mid-year meeting in conjunction with M and M again this year. The M and M meeting is to be held in Philadelphia from August 13 to 17. To this end the following resolution was submitted:

The Electron Diffraction Subcommittee recommends to the Technical Committee that the sum of $1,000 be provided so that a meeting of the Electron Diffraction Subcommittee may be held in conjunction with the Microscopy and Microanalysis meeting to be held in Philadelphia in August 2000.

8. A test of "public opinion" was made. There was a 5 to 1 (26 abstentions) opinion in favor of expanding the field of responsibility for the Subcommittee to include methods of analysis based on x-ray analysis in electron-beam instruments as well as electron diffraction. Ray Goehner intended to discuss this with ICDD authorities.

9. The meeting concluded with an example of the use of EBSD to identify small precipitates in weld affected regions.

Minutes prepared by Alwyn Eades.
4/11/00