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"Beyond Classical Rietveld Analysis using Le Bail fitting"

by Lachlan M. D. Cranswick (CCP14 Secretary, Birkbeck University of London, UK) and Armel Le Bail (Universite du Maine, France)

For presentation at IUCr 2002 - Geneva, Switzerland - M88: Beyond Classical Applications of the Rietveld Method, Thursday, August 15, 2002

[IUCr 2002 - Geneva, Switzerland]

This page is located at http://www.ccp14.ac.uk/poster-talks/iucr2002/


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Table of Contents

Beyond Classical Rietveld Analysis using Le Bail fitting

Agenda

Before Le Bail analysis "was the void"

Invention of Le Bail fitting and Le Bail Extraction

What is the Le Bail method

Some more Le Bail history

The spread and impact of the Le Bail Method

The spread and impact of the Le Bail Method -2

The spread and impact of the Le Bail Method - 3 Comparison with other methods

Some of the most complex structures solved from Le Bail method data

Some organic structures solved from Le Bail method data

Recent example

A recent application involving the Le Bail method Can there be Oxygen in the Earth’s outer core

What do we need from the data?

What do we need from the diffraction experiment

Energy Dispersive Diffraction E(keV) = 6.199 / (d_space * sin(theta_angle of Energy Dispersive detector)) Schematic Diagram

Energy Dispersive Diffraction : Advantages

Energy Dispersive Diffraction Beamline 16.4 at Daresbury X-ray Synchrotron, Cheshire, UK

Energy Dispersive Diffraction : Example of High pressure/temp. sample assembly for the multi-anvil Walker Cell

Energy Dispersive Diffraction : Example datasets at high pressure and high temperature

What do we need from the data to help us determined if there can be Oxygen in the Earth’s outer core?

Synchrotron Hardware Fixation Syndrome (SHFS)

Thus the next problem : Software Analysis: Difficulties that need to be considered:

Other Problems that need to be considered

3 x Problems that need to be overcome

Le Bail fitting is a solution!

Performing the Le Bail fit

Rietica Rietveld for Mass Le Bail fitting to get cell volumes Example of 3 phase setup : KClO3; KClO4, B2-KCl

Rietica Rietveld for Mass Le Bail fitting At simplest: 3 step process after initial setup has been done

Rietica Rietveld for Mass Le Bail fitting 1 of 10

Rietica Rietveld for Mass Le Bail fitting 2 of 10

Rietica Rietveld for Mass Le Bail fitting 3 of 10

Rietica Rietveld for Mass Le Bail fitting 4 of 10

Rietica Rietveld for Mass Le Bail fitting 5 of 10

Rietica Rietveld for Mass Le Bail fitting 6 of 10

Rietica Rietveld for Mass Le Bail fitting 7 of 10

Rietica Rietveld for Mass Le Bail fitting 8 of 10

Rietica Rietveld for Mass Le Bail fitting 9 of 10

Rietica Rietveld for Mass Le Bail fitting 10 of 10

Rietica Rietveld for Mass Le Bail : Graphing up "some" results

1. Rietica and Le Bailing : problems with stability of the Energy Dispersive Detector(?)

2. Rietica and Le Bailing : problems with stability of the Energy Dispersive Detector(?)

Using XFIT and UNITCELL for traditional Unit-cell refinement and EOS using unit weighting of HKLs http://www.ccp14.ac.uk/solution/xfit-95/ and http://www.esc.cam.ac.uk/astaff/holland/

Using XFIT and UNITCELL for EOS of NaCl and KCl : But:Le Bailing can make sure correct HKLs are assigned to the correct peaks and phases - greater than 5 phases (spurious peaks can be easily identified)

Volume of Oxygen as a function of Pressure

Implications of the volume of fluid Oxygen and the earth’s other core

Warning: a new volume of fluid oxygen at high pressure that is 50% different from the established value is up for debate

For those who believe in Shockwave / Molecular Dynamics / Impulsively Stimulated Scattering Measurements over Diffraction Methods

Summary

Author: Lachlan Cranswick

Email: l.m.d.cranswick@dl.ac.uk

Home Page: http://www.ccp14.ac.uk

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