Re: Workshop Announcement Fundamental Parameter Approach / EPDIC6

L. Cranswick ( L.M.D.Cranswick@dl.ac.uk )
Tue, 11 Aug 1998 03:44:49 +0100 (BST)

>
> Fellow diffractionists:
>
> It sounds like a hot and interesting topic in the following weeks (ECM-18
> and EPDIC-6) and is likely to continue in years to come. Just as an
> information to those interested, I'll be comparing the
> "fundamental-parameter" with "standard" approach in my talk at the EPDIC-6
> (morning of Aug 25). Of course, it won't be as detailed as we expect from
> the workshop, but maybe from a little different perspective. This comparison
> is likely to complement (and contradict ?) Armel Le Bail's remarks at the
> last week's Denver X-Ray Conference (for those not able to attend, I suppose
> that Armel made his position on this question known to this mailing list's
> audience last month).
>
> I look forward to an excellent EPDIC and exciting discussions on this issue

I think a summary is for those who can't stand the waffle
is that "it is not the best that wins - but that which is
available?"

More disoriented than usual rants about FP and Pawley/LeBail
extraction follow.

----

Hope this does not cause me to miss my early morning
plane to Prague - am attending the Space Group workshop.
(Monte Carlo search method will then be implemented for
finding the Space Group Workshop course registration area
(assuming they have received the cheque from the Lab ADMIN))

----

While EPDIC could thus be very interesting on the
Fundamental Parameters front (the law will be laid down????) -
Personally, I believe the time is right for this approach
given the algorithsm and computational power are almost up
to it.

Though it is most likely that people will still be using
mathematical fitting due availability of code being the
major factor(?).
A major superiority of the Finger, Cox, Jephcoat, (J. Appl. Cryst.
27, 892, 1992) asymmetry correction is (thanks to the authors)
the code is available in forms that can be implemented into
existing software.
ftp://cryst.ciw.edu/profile/
http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/larryfinger/PROFILE/
(pascal, fortran and c code)

----

Another possibility for a major comeback(?) given computer
power (and maybe fundamental parameters profiling) is the
Pawley method over the LeBail method(?) Given (still have to
find the right references here) the benefits of having
ESDs combined with the covarience matrix(?) - when appropriately
applied - should be an advantage in Direct Methods, Patterson
and Direct Space Structure solution methods of LeBail extraction?

Though the problem there is that it only takes around a
day to implement the LeBail method and the information to
implement this is readily available:
http://www.ccp14.ac.uk/solution/lebail/

However try to find code or methods for implementing Pawley
into existing programs - and even more obscure(?) -
available programs that can use the extra information
it provides for structure solution?
http://www.ccp14.ac.uk/solution/pawley/

It seems quite useless at present to use Pawley
over LeBail extraction if there is
no software that can make better use of the Pawley data?

Conclusion - Le Bail will be used over Pawley method well
into the next Millenium? Same goes with Empirical peak
fitting over Fundamental Parameters?

---

Though I am not obverse to letting the evidence guide here -plus I will be in direct throttlable distance at ECM and EPDICso see you there for an interesting time!

Lachlan.

PS: If there are programs "available" on the internetthat can "USE" the Pawley data for structure solution inits various forms - would be keen to find out about them.If no website - CCP14 can find a friendly home for them(and anything crystallographic) at: http://www.ccp14.ac.uk/

> > Best regards to all,> > Davor Balzar> balzar@nist.gov`> > > -----Original Message-----> From: Arnt.Kern@bruker-axs.de <Arnt.Kern@bruker-axs.de>> To: Rietveld_l@ill.fr <Rietveld_l@ill.fr>> Date: Monday, August 10, 1998 4:27 AM> Subject: Workshop Announcement Fundamental Parameter Approach / EPDIC6> > > >---------- Second Announcement ----------> >> >The Bruker-AXS GmbH cordially invites you to the following workshop, which> >will be held as a satellite meeting accompanying the 6th EPDIC conference> in> >Budapest:> >> >"A New Fundamental Parameters Approach in Profile Analysis of Powder Data"> >> >Dr. A. Kern, Dr. A. Coelho, Dr. T. Taut> >> >-----> >> >The topics to be discussed are:> >1. Possibilities and limits of recent profile analysis techniques> >2. Fundamental parameter approach vs. conventional fitting techniques> > a) Principles & core mathematics> > b) Generation of line profiles> > c) Emission profile, instrument characterisation, sample contributions> >3. STANDARDLESS real structure analysis (crystallite size, microstrain,> >absorption, ...)> >4. Instrument characterisation (axial divergence, horizontal divergence or> >flat specimen, slit dimensions, ...)> >5. Use of any parameter couplings and of any constraints (linear and> >non-linear)> >6. "How many peaks are there?"> >7. Instrument alignment aspects> >8. Software> >> >----------> >> >Date:> >Monday, 24. August, 16:30 - 18:30.> >> >Workshop language is ENGLISH.> >Participation is free.> >> >Please register at the Bruker-AXS booth.> >> >----------> >> >For further information please contact:> >> >Dr. Arnt Kern> >Bruker-AXS GmbH> >Oestliche Rheinbrueckenstr. 50> >D-76181 Karlsruhe> >> >Fax: ++49-721-595-6693> >EMail: Arnt.Kern@bruker-axs.de> >> >> >> >********************************************> >Dr. Arnt Kern> >Bruker AXS GmbH> >AXS M> >Östliche Rheinbrückenstr. 50> >76187 Karlsruhe> >Germany> >Tel.: (+49) 721-595-5669> >Fax: (+49) 721-595-6693> >EMail: Arnt.Kern@bruker-axs.de> >URL: http://www.bruker-axs.de> >********************************************> >> >> >> >> > >

-- Lachlan M. D. CranswickCollaborative Computational Project No 14 (CCP14)    for Single Crystal and Powder DiffractionDaresbury Laboratory, Warrington, WA4 4AD U.KTel: +44-1925-603703  Fax: +44-1925-603124  E-mail: l.cranswick@dl.ac.uk  Ext: 3703  Room C14NEW CCP14 Web Domain (Under heavy construction):                           http://www.ccp14.ac.uk