"Beyond Classical Rietveld Analysis - using Le Bail fitting of X-ray Powder Diffraction data to help answer the questions of the world: can the Earth's outer core contain Oxygen?"

Lachlan M. D. Cranswick CCP14 (Collaborative Computation Project No 14 for Single Crystal and Powder Diffraction) Department of Crystallography; Birkbeck University of London, Malet Street, Bloomsbury, London, WC1E 7HX, UK. E-mail: [email protected] WWW: http://www.ccp14.ac.uk

Talk Emphasis

• • • Solving relevant problems in the various sciences such as the geosciences may require an intimate and non-routine knowledge of possible analytical techniques and their use You may have to obtain more information that you initially wante to know.

In this case: – – Energy Dispersive Powder X-ray diffraction (EDX) and Le Bail fitting. • (named after its inventor, Armel Le Bail of the Laboratoire des Fluorures, CNRS, University of Le Mans, France) Slide 2 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Agenda

• • • • • An attempt at explaining “Le Bail fitting” to the non diffractionist Was there anything before Le Bail Analysis?

Invention of Le Bail fitting and Le Bail extraction The spread and impact of Le Bail fitting A modern application of the Le Bail method : Does the Earth’s outer core contain oxygen (determining the volume of fluid Oxygen at high temperature and pressure) Slide 3 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietveld refinement

• • A method devised in the late 1960’s by Hugo Rietveld at the Reactor Centrum Nederland, The Netherlands to perform crystal structure refinement on the entire powder diffraction pattern profile.

– http://home.wxs.nl/~rietv025/ The required crystal structure information is: – Unit Cell – Spacegroup – Starting Atomic Positions Slide 4 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietveld fitting/refinement

• Combined X-ray / Neutron Rietveld refinement Slide 5 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Le Bail fitting

• • • Le Bail fitting is just doing a Rietveld fit without the atomic information being present The required crystal structure information is: – Unit Cell – Spacegroup All the HKL intensities can freely vary (though are constrained not to be negative - and a few other rules applied - “equi-partitioning”) Slide 6 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Le Bail fitting

Slide 7 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Applications of Le Bail fitting

• Can quickly obtain HKL intensities for attempting to solve a structure from powder diffaction data (the extracted HKL data can then be treated as a single crystal dataset) • • •

Unit Cell refinement using the whole diffraction profile

Spacegroup determination Extract intensities of a pure phase for structureless Rietveld quantitative phase analysis (where the unitcell is known) Slide 8 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Before Le Bail analysis “was the void”

•

Not exactly - 1981 Pawley method -

– "Unit-cell refinement from powder diffraction scans", (G.S. Pawley J. Appl. Cryst. 14 (1981) 357-361) (University of Edinburgh) • Unlike Le Bail fitting - in a Pawley fit, each HKL is a parameter in the least squares fitting matrix.

• • Not easily implemented in existing Rietveld software When developed, was not matched up with the weak computer power due to each HKL being a parameter in the least squares matrix (1000 HKLs and 10 pattern/profile parameters = 1010 x 1010 least squares matrix) • Available early implementations had a reputation of being unstable and difficult to control • Only relatively recently that methods have improved to make the Pawley method a going concern and rival in usability to Le Bail method (all are restricted access and/or commercial(?)) Slide 9 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Invention of Le Bail fitting and Le Bail Extraction

• • From Armel Le Bail: – – – July 1987 “came during a long and lonesome night experiment at ILL (Institute Laue-Langevin, Grenoble, France)” - neutron diffraction “It seemed so simple that my first thought was that probably either it was already done or it did not work at all. But at least everybody used it successfully for only one cycle when extracting the so-called "|Fobs|" at the end of any Rietveld refinement. These "|Fobs|" being used for R-Bragg calculation and Fourier difference purposes though it was long recognized that they were biased due to partitioning according to the Fcalc, hence the quotes.” A Rietveld program author can code this in less than 30 minutes (at least in the case of the Rietica Rietveld) Slide 10 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

The spread and impact of the Le Bail Method

• Main impact has been in crystal structure solution from powder diffraction data by extracting HKL intensities • Number of published structures solved by powder methods • Cumulative total of 592 up to end of 2001 Slide 11 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

Totals

Le Bail = 134 Pawley = 43 No cell constraint = 49 Other / Unspecified = 92 Slide 12 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

1992 - Nature 359, 519-522 SYNCHROTRON + NEUTRON R.E. Morris, W.T.A. Harrison, J.M. Nicol, A.P. Wilkinson & A.K. Cheetham Ga 2 (HPO 3 ) 3 .4H

2 O 29 independent atoms, 86 coordinates refined 1993 - J. Solid State Chem. 103, 287-291 A. Le Bail  -Ba 3 AlF 9 CONVENTIONAL X-RAY 29 independent atoms, 74 coordinates refined 1994 - J. Solid State Chem. 111, 52-57 SYNCHROTRON + NEUTRON R.E. Morris, J.J. Owen, J.K. Stalick & A.K. Cheetham La 3 Ti 5 Al 15 O 37 60 independent atoms, 178 coordinates refined Slide 13 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Some organic structures solved from Le Bail method data

1998 - Fluorescein Diacetate K. D. Knudsen, P. Pattison, A. N. Fitch, R. J. Cernik Angew. Chem. Int. Ed. 37 (1998) 2340-2343. C24H16O7 Solved by direct methods (EXTRA/Sirpow) 2000 - The Structure of Malaria Pigment (beta-Haematin), S. Pagola, P. W. Stephens, D. S. Bohle, A. D. Kosar and S. K. Madsen, Nature, 404 (2000) 307-310.

Solved by simulated annealing (PSSP) Slide 14 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

So many unknown mineral structures?

From the IUCr Commission on Powder Diffraction Newsletter (July 2002): http://www.us.iucr.org/iucr-top/comm/cpd/Newsletters/no27jul2002/

Armel Le Bail: ‘

Finding a Mineral Problem to Solve ’ (Page 24)

“Thus, a list of more than 300 minerals with probably unknown CS [Crystal Structures] was established”

Slide 15 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Recent example

(Mg,Fe 2+ ) 3 (Al,Fe 3+ ) 4 (PO 4 ) 4 (OH) 6  2H 2 O

Gormanite

Triclinic 19 independent atoms Solved by direct space method (ESPOIR) from 500 extracted structure factors Synchrotron data In spite of 3 impurities (10% of the sample) A. Le Bail, P.W. Stephens, F. Hubert, European Journal of Mineralogy, 2003, 15 Slide 16 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Using Le Bail fitting for unit cell refinement

• •

Not as hyped up as the extraction of HKL intensities for structure solution, but very powerful and speedy.

Can perform unit cell refinement in seconds - rather than minutes and hours as when using traditional single peak fitting and unit cell refinement methods.

A. Le Bail, P.W. Stephens, F. Hubert, European Journal of Mineralogy, 2003, 15 Slide 17 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• Project headed by Professor Dave Walker of the Lamont-Doherty Earth Observatory of Columbia University, New York, USA • Use energy dispersive X-ray diffraction; and high pressure / high temperature phase transitions to help determine the volume of fluid Oxygen at high pressure and temperature (~550°C and 2 to 9 GPa) . Then see if the volume this has interesting implications for Oxygen being involved in the Earth’s Outer Core Slide 18 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• •

Why ask the question: Can there be Oxygen in the Earth’s outer core

The currently accepted value for the “volume of fluid oxygen” at high pressures and temperatures is too large for it to exist interstitially within the metal liquid of the earth’s outer core (Established Volume of Oxygen ~15 cc / mol) However, some anomalous results from a variety of different sources -diamond cell (Knittle and Jeanloz; Goarant, et al), isotope analyse from plume type volcanics (Osmium isotopes) can be interpreted in the framework of: – – There being a smaller “volume of oxygen” that can interstially fit within the metal liquid of the earth’s outer core; That the earth’s outer core is already oxygen saturated (possibly in the form of an oxide liquid), and the outer core is exsolving as it cools down. – As it hits the colder base of the mantle, the exsolving oxygen preferentially takes with it some elements in perference to others (Siderophile elements: Iron, Nickel, Cobalt - and Osmium) – These effects are potentially showing up in some plume type volcanics Slide 19 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• • •

What is wrong with the previous determinations of the volume of Oxygen

The established “volume of oxygen” determinations (mainly using shockwave techniques) involve large extrapolation distances - which could be providing a non-optimum results. (25,000 Celcius at 800 kbar). Or shockwave has locked into a wrong phase of Oxygen.

– Laura Robin Benedetti, Molecular systems at high pressures and temperatures: Solar system astronomy in a physics laboratory, Ph.D. thesis, Physics Dept., Univ. of Calif., Berkeley, 2001.

Thus try and use a different approach developed by Professor David Walker at Columbia University to obtain the volume of fluid Oxygen in a temperature and pressure regime closer to that of the inner earth.

Slide 20 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

What do we need from the diffraction data?

Accurate Unit Cell volumes

the “equations of state” to obtain (EOS) of the phases of interest

(how the volume of the phases change with pressure and temperature) T - RbClO 4

=

B2-RbCl + 2O 2 4 R-KClO3 = 3 O-KClO4 + B2-KCl O-KClO4 = B2-KCl + 2 O2

O 2 from the differences in the unit cell volumes Thus use powder X-ray diffraction Slide 21 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

What do we need from the diffraction experiment

• Ability to penetrate high a “large volume” high pressure cell - high temperature cell (in this case a multi-anvil Walker Cell) • Ability to get the X-ray beam in and out of tight spaces • Thus synchrotron based Energy Dispersive Diffraction can be advantageous for these types of problems.

Slide 22 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Energy Dispersive Diffraction

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

Schematic Diagram

Collimator and EDX detector – at a fixed angle (stationary) White X_ray Beam Slide 23 Sample Environment Diffraction patterns are obtained only of the volume subtended by the collimator with the incident X-ray beam Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Energy Dispersive Diffraction : Advantages

• • • Unlike conventional single wavelength XRD, EDX can see “inside” unconventional sample environments – Within limits: can have steel or other materials shielding the sample at pressure and/or temperature • • thus samples can also be immersed in gas or liquid (hydrothermal synthesis) in-situ studies - reactions / explosions / properties under stress. Particle flows within gases and fluids. Reactions in gas/fluid flow lines.

• Only see diffraction in the volume (nick-named the “lozenge”) defined where the detector collimator subtends onto the incident white X-ray beam Spatial Resolution inside the sample environment – Can narrow down the beam and collimator - and move the sample : thus obtaining diffraction patterns from different spatial volumes inside the sample environment Fast data collection times – minutes to fractions of a second Slide 24 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Energy Dispersive Diffraction

Beamline 16.4 at Daresbury X-ray Synchrotron, Cheshire, UK

• In high pressure mode and Walker Cell and Press installed • All the hardware can make for a crowded and complicated environment.

• Can require a lot of effort and concentration to get the X-ray beam pointing at the right areas of the sample.

Slide 25 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Energy Dispersive Diffraction :

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

Slide 26 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Energy Dispersive Diffraction :

Example datasets at high pressure and high temperature

Slide 27 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • What do we want?

– “Accurate” Unit-cell volumes to obtain equations of state (EOS) When do we want it?

– Now!! - and/or in a timely fashion (not 6 months to 5 years later!) Slide 28 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Synchrotron Hardware Fixation Syndrome

(SHFS)

• • • Diagnosis: – A neurotic spending of all effort on custom novel synchrotron hardware without consideration and similar effort put into software analysis requirements Effects: – Beamlines can have very low productivity due to data analysis being unnecessarily problematic and taking months or years of analysis (kludging together a software solution) (Can also be a problem with venders manufacturing mass raw data generators: e.g., specialist laboratory XRDs and mapping Microprobe systems) Slide 29 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • • • Energy Dispersive Diffraction setup and calibration can be very ad-hoc and problematic Possible Detector instability over short time spans Possible “other” detector problems (more neurotic of these problems only obvious when doing whole pattern Le Bail fitting) Slide 30 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Other Problems that need to be considered

• • • Poor resolution data with multiple sources of spurious peaks (fluorescences, hitting non-sample parts of the sample assembly, etc) Phase transitions giving unknown cells (need powder indexing - different talk) Track how diffraction patterns are changing through the experiments Slide 31 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

3 x Problems that need to be overcome

• • • Overlapping multi-phase powder patterns Large amounts of raw diffraction data! (collecting 3 patterns each 5 to 300 seconds) Intensities are near meaningless – – – – no incident intensity spectrum particle statistics problems preferred orientation problems X-ray absorption Slide 32 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Le Bail fitting is a solution!

• • Peak numbers and shifts are constrained by cell and spacegroup • • • • Le Bail method does not care about X-ray intensities Can handle multiple phases Is graphical in modern software Speedy and easy (very important when you have 100’s to 1000’s of XRD patterns) Impurities and spurious peaks are often very obvious Slide 33 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Performing the Le Bail fit

• Rietica Rietveld for Windows by Brett Hunter at ANSTO neutron reactor facility (Sydney, Australia) – http://www.rietica.org/ - is free software –

Newish:

Easy to use mass Le Bail fitting of angular and energy dispersive data – All files are ASCII Files – – Handles alpha 1 /alpha 2 (if relevant) Flexible : can manually edit Le Bail ASCII HKL files to delete reflections • Powerful option when dealing with overlapping phases and multiphase samples where trace peaks of one phase can overlap with major peaks of another.

– Macro language that can fully automate the routine parts of the data analysis (still under development).

Slide 34 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • • Easy to use and setup via GUI Easy to add and delete structures Database for adding and recalling structures / unit cells Slide 35 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • • Some EDX beamlines give the option of converting into 2-theta space or refining native in KeV (2-theta can be convenient for using search match and related software - SHFS again) Le Bailing Sequence: 1. Copy over INP and HKL file (using windows explorer) 2. Perform whole profile LB fit 3. Evaluate / plot results - (check need to add or delete phases) 4. Repeat above Slide 36 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail fitting 1 of 10

• Before the phase transition - only Potassium Chlorate is present Slide 37 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• In the phase transition

Rietica Rietveld for Mass Le Bail fitting 2 of 10

• No completely freestanding peak for KCl Slide 38 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail fitting 3 of 10

• Repeat as required • No completely freestanding peak for KCl Slide 39 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail fitting 4 of 10

• Repeat as required • No completely freestanding peak for KCl Slide 40 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail fitting 5 of 10

• Repeat as required • Still no completely freestanding peak for KCl Slide 41 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• Repeat as required

Rietica Rietveld for Mass Le Bail fitting 6 of 10

Slide 42 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• Repeat as required

Rietica Rietveld for Mass Le Bail fitting 7 of 10

Slide 43 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• Repeat as required

Rietica Rietveld for Mass Le Bail fitting 8 of 10

Slide 44 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

• Repeat as required

Rietica Rietveld for Mass Le Bail fitting 9 of 10

Slide 45 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail fitting 10 of 10

•

Done!!!

• Just have to repeat for a few more 100 to few 1000 datasets Slide 46 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Rietica Rietveld for Mass Le Bail : Graphing up “some” results

Using Traditional Methods Using Le Bail fitting Slide 47 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • NaCl / Halite at Room Temperature and Pressure (thus is not crystal strain) Very nasty miss-fits on peak positions • • • Possible instability in the detector Peaks cause detector to become unstable in the region of high counts(?) Other problems?

Slide 48 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

Le Bail fitting Non-unit weighting of reflections Isotherm data of different temperatures colliding Inappropriate to use Le Bail fitting on this data Though Le Bail can detect these problems on the beam-line!!

Traditional Unitcell refinement Unit weighting of reflections (over a wide KeV range - the data is “on average” linear) Isotherm data no longer overlapping Slide 49 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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/

Slide 50 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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)

Slide 51 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Volume of Oxygen as a function of Pressure

• Energy Dispersive XRD: vol O 2 ~10 cc/mol • Established vol O 2 from shockwave experiments: ~15 cc/mol (50% difference) • The full scientific logic going from the equations of state (EOS) to earth’s outer core would require a separate talk by Dave Walker.

Slide 52 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• 15 cc/mol means there cannot be Oxygen in the Earth’s outer core (the results from shockwave / molecular dynamics) • 10 cc/mol (EDX result) means there can be Oxygen in the Earth’s outer core - and has implications for “outer core” “lower mantle” interactions Slide 53 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• • • When submitted to the journal Science with the suggestion that these diffraction results be taken as seriously as the shock wave results, because the new results disagree with the dynamic techniques, 2 out of 3 reviewers believed this to be dangerous nonsense, from which the community deserves protection.

"Synthesis and thermal decomposition of tetragonal RbClO4 and volume of fluid O2 from 2 to 9 GPa" D. Walker, G. Hughes, L. M. D. Cranswick, S. M. Clark, and S. Buhre, Geochemistry, Geophysics, Geosystems (G 3 ) Vol 2, October 2001. (http://g-cubed.org/) "O2 volumes at high pressure from KClO4 decomposition: D" as a siderophile element pump instead of a lid on the core." D. Walker , S.M. Clark, L.M.D. Cranswick, M.C. Johnson, R.L. Jones, Geochemistry, Geophysics, Geosystems (G 3 ), 23 November 2002. (http://g-cubed.org/) Slide 54 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

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

• Is possible that dynamic methods : – Have problems with systematic errors in the extrapolation – Are accurate but have locked into an inappropriate phase of Oxygen Slide 55 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk

Summary

• • • • • Having a full appreciation of the variety of analytical methods and data analysis techniques may be important for obtaining effective results within a much larger scientific project.

The Le Bail method allows the time effective high quality fitting of masses of powder X-ray diffraction data (relevant for following phase transition / high temperature / high pressure experiments) (possibly appreciating the iniquity of Synchrotron Hardware Fixation Syndrome (SHFS)) Le Bail method full saga webpage: http://sdpd.univ-lemans.fr/iniref/lbm-story/ Other information about the Le Bail method at: http://www.ccp14.ac.uk/solution/lebail/ Slide 56 Using diffraction methods to solve the problems of the world Lachlan M. D. Cranswick ([email protected]) http://www.ccp14.ac.uk