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"Re-stating the obvious: To solve structures from powder diffraction, first they must be indexed!"

by Lachlan M. D. Cranswick (CCP14 Project Secretary, UK) and Robin Shirley (Surrey University, UK)

For presentation at ACA 2002 - San Antonio, Texas, USA - TR.01: Crystal Structure Determinations from Powder Diffraction Tuesday, May 28 - 08:30 - 09:00 AM

[ACA 2002, San Antinio, Texas, USA]

This page is located at http://www.ccp14.ac.uk/poster-talks/aca_2002b/


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Table of Contents

Re-stating the obvious: To solve structures from powder diffraction, first they must be indexed!

Notes Free Zone - they are on the web http://www.ccp14.ac.uk/poster-talks/aca_2002b/

Talk Aims

Some History of Powder Indexing

Some History of Powder Indexing - 2

Some History of Powder Indexing - 3

Checking Sample Purity

Peak Profiling Software

Empirical peak fitting : Some tricks may be required for stability and reasonable results

Peak Profiling: high accuracy peak positions using Fundamental Parameters peak profiling

XFIT Fundamental Parameters Peak Profiling mode : fit to a low angle peak on a Bragg-Brentano diffractometer

Powder Indexing FOM Results XFIT Fundamental Parameters peak profiling compared to empirical Peak Fitting

Powder Indexing - indexing programs

Powder Indexing - indexing suites

Powder Indexing - specialist programs

Powder Indexing - the Crysfire suite (1)

Powder Indexing - the Crysfire suite (2)

New Release - Crysfire 2002

Why bother running more than one powder indexing program?

Powder Indexing - Routine Crysfire Example Importing an XFIT peak file with xf2crys, to give a Crysfire CDT file

Powder Indexing - Routine Crysfire Example - Run crysfire (giving the following screen)

Powder Indexing - Routine Crysfire Example - "lo" to load a CDT file

Powder Indexing - Routine Crysfire Example - "sa" to target an indexing program

Powder Indexing - Routine Crysfire Example - target ITO with defaults

Powder Indexing - Routine Crysfire Example - "in" to start the targetted program running ITO

Powder Indexing - Routine Crysfire Example - ITO runs

Powder Indexing - Routine Crysfire Example - After Ito completes, press enter to see output file

Powder Indexing - Routine Crysfire Example - Then "enter" again to see "one solution per line" summary

Powder Indexing - Routine Crysfire Example - "Enter" again to see Le Page summary of reduced cells

Powder Indexing - Routine Crysfire Example

Powder Indexing - Routine Crysfire Example Finally: the complete summary file - 3332 trial solutions

Powder Indexing - Routine Crysfire Example Complete Le Page summary file of reduced cells - 3332 trial solutions

Crysfire Self Calibration Bragg-Bretano Data

Crysfire Self Calibration Example

Crysfire Re-scaling Protein Data (from Bob von Dreele)

Chekcell: Interpreting Crysfire Summary Files: Powder Indexing and Spacegroup Assignment

Chekcell : easy to see non-matching or impurity peaks

Chekcell : automatic cell and spacegroup searching

Chekcell: "integration" of Ton Spek and A. Meetsma’s Le Page - (Crysfire 2001 now also provides a reduced-cell summary)

Chekcell: GUI Cell transformation

Chekcell: Density / Z/ Mol. Vol explorer

Chekcell: example of it running - Load the raw diffraction data

Chekcell: example of it running - Load the peak position file

Chekcell: example of it running - Load the Crysfire summary file

Chekcell: example of it running - Use the tools to evaluate the trial cells

Crysfire / Chekcell: indexing powder Protein data

Crysfire / Chekcell: indexing powder Protein data

MMAP

MMAP - what does the output look like?

MMAP

MMAP - which of these objects is man made? - Using peak height as the selection criteria.

MMAP - which of these peaks is man made? 2

Analogous problem with powder indexing

An Mmap landscape

Mmap

Mmap

Mmap : Is the following a good solution?

Mmap : Yes looks a good solution

Mmap : Is the following a good solution?

Mmap

Mmap: Is the following a good solution?

Mmap

Mmap

Conclusion

Author: Lachlan Cranswick and Robin Shirley

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

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

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