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Structure solution fromStructure solution from(high pressure)(high pressure)

powder diffraction datapowder diffraction data

Yaroslav Filinchuk SNBL @ ESRF

www.filinchuk.comwww.snbl.eu

Erice, 4 – 14 June 2009

workshop preview

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Powder diffraction with a 2D detector

Problems of Problems of powder powder

diffractiondiffraction

Keep this Keep this picture in picture in

mind when mind when using 1D using 1D detectorsdetectors

Y. Filinchuk Erice, 4-14 June 2009

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Powder diffraction: needs and posibilities

… this was the case of a simple structure and good data

• to identify a phase

• to attribute data to a known structure type (indexing suffice)

• to refine a known structure

• to solve it from scratch (ab initio structure solution)

• to observe T or P-variation

• to monitor a chemical reaction (time resolution)

• Combination of allCombination of all: new phases, transitions, evolution…

Data can be good or bad, or in between...

Y. Filinchuk Erice, 4-14 June 2009

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Essential programs

FullprofFullprof: Rietveld refinement, simulation of powder data, data

manipulation and program shell (WinplotrWinplotr)

Dicvol, ChekcellDicvol, Chekcell: indexing rearch for the true cell

FOXFOX: structure solution in the direct space (“trial and errror”)

PowderCellPowderCell: generation of sub- and superstructures

PlatonPlaton: search for a true symmetry, for voids, “problems”

MercuryMercury,, Diamond Diamond: visualization, analysis of coordination

polyhedra, ineratomic distances, topology

DatabasesDatabases: International Tables (Vol. А), ICDD, ICSD, …

Y. Filinchuk Erice, 4-14 June 2009

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Problems tackled

• indexing

• structure solution from “bad” powder data

• using chemical knowledge in solving structures

• dealing with severe texture during structure solution

• finding higher metric or crystallographic symmetry

• refinement by the Rietveld method

Y. Filinchuk Erice, 4-14 June 2009