Apr 302012
 

J Appl. Cryst. (2012), 45, 417-429. [ doi:10.1107/S0021889812015191 ]

Leverages measure the influence that observations (intensity data and restraints) have on the fit obtained in crystal structure refinement. Further analysis enables the influence that observations have on specific parameters to be measured. The results of leverage analyses are discussed in the context of the amino acid alanine and an incomplete high-pressure data set of the complex bis(salicylaldoximato)copper(II). Leverage analysis can reveal situations where weak data are influential and allows an assessment of the influence of restraints. Analysis of the high-pressure refinement of the copper complex shows that the influence of the highest-leverage intensity observations increases when completeness is reduced, but low leverages stay low. The influence of restraints, notably those applying the Hirshfeld rigid-bond criterion, also increases dramatically. In alanine the precision of the Flack parameter is determined by medium-resolution data with moderate intensities. The results of a leverage analysis can be incorporated into a weighting scheme designed to optimize the precision of a selected parameter. This was applied to absolute structure refinement of light-atom crystal structures. The standard uncertainty of the Flack parameter could be reduced to around 0.1 even for a hydrocarbon.

Electronic reprints

Publisher’s copy

Apr 202012
 

The 2012 Meeting of the British Crystallographic Association was held at Warwick University.  Oxford was very well represented this year with Kirsten Christensen chairing the Programme Committee and prizes being awarded to Joe Paddison, Nick Funnell and Emma McKinley.

Other contributions from Oxford include:

Karim J. Sutton, Kirsten E. Christensen, Amber L. Thompson & Richard I. Cooper
Exploiting the Tunable Wavelength Capabilities of I19 (Poster & Oral Presentation)

Callum A. Young & Andrew L. Goodwin
An Examination of the Low Temperature Structure of Fe3O4 Using Reverse Monte Carlo Refinements (Oral Presentation)

Andrew L. Goodwin
Frameworks, Flexibility and Frustration (Oral Presentation)

Kirsten E. Christensen, Amber L. Thompson & Arwen R Pearson
Discussion Forum:  From Small Molecules to Proteins:  Bridging the Gap

Emma J. McKinley, Kirsten E. Christensen & Amber L. Thompson
Investigation of the Transient Modulated Phase of Barluenga’s Reagent (Poster)

Andrew B. Cairns, Amber L. Thompson, Andrew L, Goodwin, Matthew G. Tucker & Julien Haines
Anomalous Compression of Cyanide Frameworks:  Mechanisms for Extreme Negative Response (Poster)

Callum A. Young, Edward Dixon, Michael A. Hayward & Andrew L. Goodwin
Apical Oxygen Bonding in YBCO – A Reverse Monte Carlo Approach (Poster)

Ines E. Collings, Andrew B. Cairns, Amber L. Thompson, Andrew L, Goodwin, Philip Pattison, Julien Haines, Matthew G. Tucker, Julia E. Parker & Chiu C. Tang
Transferable Mechanics in Molecular Framework Materials (Poster)

Joseph A. M. Paddison, Andrew L. Goodwin, Ross Stewart, Pascal Manuel, Matthias J. Gutmann, David A. Keen, Matthew G. Tucker, Andrew Wildes & Brian Rainford
Frustration and Magnetic Diffuse Scattering in β-Mn0.8Co0.2 and MnO:  A Reverse Monte Carlo Study (Poster)

Matthew Cliffe & Andrew L. Goodwin
Disorder and Defects in Zirconium MOFs (Poster)

Nicholas P. Funnell, Martin T. Dove Andrew L. Goodwin Simon Parsons & Matthew G. Tucker
How Molecules Prepare to Undergo a Transition:  The Onset of Disorder in Solid Cyclohexane (Poster).

 

Karim speaks to the Young Crystallographers

Karim speaks to the Young Crystallographers

 

Emma, Richard and Ines go to the conference dinner

Emma, Richard and Ines go to the conference dinner

Ines and Emma

Ines and Emma

This time Karim brought his Dad...

This time Karim brought his Dad…

Callum and Emma at Dinner

Callum and Emma at Dinner

Kirsten presents Nick with his prize

Kirsten presents Nick with his prize

Emma receives her prize

Emma receives her prize

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Contemplating Fourier Transforms...

Contemplating Fourier Transforms…

Apr 202012
 

My poster is all about Barluenga’s Reagent,
A cool iodinating and oxidising agent.
It is known to have a solid-state transition,
But we didn’t know at what temperature position.

Variable temperature X-ray diffraction
Let us investigate the transition action.
In addition, we found something a little surprising,
Extra reflections in precession images were arising.

After some thinking we came to the conclusion,
A transient modulated phase must be the solution.
So if this poem has got you excited,
Come and see my poster…

…You are all invited!

E. J. McKinley
BCA 2012.

Emma receives her prize

Emma receives her prize