Jul 132010

Cryst. Rev. (2010), 16(3), 197-230.    [ doi:10.1080/08893110903483246 ]

X-ray single crystal structure analysis has become a gold standard for the determination of molecular geometry. The reliability of the technique is a triumph for science and technology working together. The uniqueness of well-crystalline material intrigued early natural philosophers, and their examinations, followed by the discovery of the diffraction of X-rays by crystals, led to the powerful technology that we now enjoy. For about three quarters of a century molecular structure determination has been a driving force for crystallographic research, but now that the science has matured into a technology, interest is returning in trying to understand the nature of crystals themselves.

Jul 012010

There is some really cool chemistry done in Oxford and some even cooler structures.  In order to encourage everyone to take an interest in what other people are doing with our instruments, we have instigated a “Structure of the Month”.  The idea is that users submit a single-crystal structure that they have done (either here or at Diamond/ISIS).  This is done by filling in a form including a short explanation of why it is cool and we will choose the best submission and stick it up in the lab in an obvious place.

The rules are as follows:

In order to keep it current, the structure must have been collected in the previous two months, i.e. the structure for October must have been collected in August or September (or where the work is particularly sensitive, “accepted for publication” in the previous month).

  • The competition is only open to affiliates of Oxford Chemistry
  • We must receive it by email before the end of the previous month, i.e. submissions for October must be received by the end of September.
  • You must include a colour picture.
  • The description must be 100 words or less (we are very strict about this).
  • It must be cool to you, but it can be cool for any reason (see below).
  • The Judges’ decision is final.

You should include a covering comment explaining why it is cool to you.  We will accept most reasons, but examples include:

  • “It’s taken me three years to make it, 200 attempts to crystallise it and 10 days of data collection time, but we got it in the end.”
  • “We crystallised Vac Grease!”
  • “It has an R1 < 1%” (or even “it has an R1 > 35%”).
  • “How on earth did we make that???”
  • “We got an invitation to Stockholm to collect an award because of it…”
  • “I’ve collected 300 datasets and done structures for everyone else in my group, but this was the first one for me.”
  • “It is the first/longest/largest/… example of…”
  • “It’s just a cool molecule”.

If we have no submissions for one month, we will look back over submissions for the previous month and earlier until we find something suitable.

The decision will be based on “coolness”, but we will endeavour to ensure that there is plenty of variety too.  The Judges’ decision is final.  In time, there will be a small trophy that the winner can look after for a month while they are the holder.  For confidentiality reasons, the winning entry will be displayed at the entrance to Chem. Cryst. and will only be reported on the website once it has been published.

Please stick to the template and keep it to a single full page as in the example.  Email submissions to Dr. Amber L. Thompson by the end of the month; late submissions will be entered for the following month.

Jun 292010

J. Appl. Cryst. (2010), 43, 1100-1107.    [ doi:10.1107/S0021889810025598 ]

Because they scatter X-rays weakly, H atoms are often abused or neglected during structure refinement. The reasons why the H atoms should be included in the refinement and some of the consequences of mistreatment are discussed along with selected real examples demonstrating some of the features for hydrogen treatment that can be found in the software suite CRYSTALS.

Hydrogen addition in CRYSTALS

Hydrogen addition in CRYSTALS

Electronic reprints:

Publisher’s copy:

Jun 152010

Dr David Watkin, an Honorary Member of the BCA, has been awarded the 2010 Fankuchen Award by the American Crystallographic Association. The award recognizes contributions to crystallographic research by one who is known to be an effective teacher of crystallography.

The Award will be presented at the ACA Annual Meeting in New Orleans 2011 at which David will also be delivering a Plenary Lecture.

Apr 152010

Cryst. Rev. (2010), 16(2), 133-144.    [ doi:10.1080/08893110903483238 ]

Recent developments in crystallographic error analysis are described. This report provides an introduction to more-formal work, originally published in Ref. (Haestier, J., J. Appl. Cryst. 2009, 42, 798). Prior to the main discussion, a brief overview of the normal distribution and error-propagation is provided, with some simplified examples to demonstrate the effects of covariance terms on error calculations. A new method is described for absorbing the cell-parameter errors into the variance-covariance matrix of the refined parameters. Problems occur for monoclinic and triclinic cell settings as the crystallographer must ‘choose’ how errors on the cell angles affect the coordinates. The choice has no effect on error-calculations on the internal geometry (bond-lengths, angles and torsion angles) of the structure, but may introduce a bias if the errors are used as weights.

Apr 152010
Susan Huth presents Kirsten Christensen with the Durward Cruickshank Award

Susan Huth presents Kirsten Christensen with the Durward Cruickshank Award

The final dinner of the British Crystallographic Association Spring Meeting in Warwick was interrupted, as always, with the prize winning awards. Amber Thompson was awarded the International Union of Crystallography Prize (a copy of International Tables) for her explanation of the advantages of choosing non-standard space groups. Kirsten Christensen was awarded the Durward Cruickshank prize for a young crystallographer who had made an outstanding contribution to crystallography.



Other contributions include:

N. David Brown, James Haestier, Mustapha Sadki, Amber L. Thompson & David J. Watkin
matchbOx:  Automatic Structure Matching to Facilitate Crystallographic Refinement (YC Presentation)

Kirsten E. Christensen, Christopher J. Serpell, Nicholas E. Evans & Paul D. Beer
Pushing the Boundaries of Small Molecule Crystallography:  The Challenging Structure of a Macrocyclic Anion Sensor (Poster)

Richard I. Cooper, Amber L. Thompson & David J. Watkin
The Hydrogen Challenge:  Where are we Now? (Poster)

Christopher J. Serpell & Paul D. Beer
Refinement of Large Supramolecular Structures (Presentation)

David J. Watkin
Dealing with Difficult Data (Session Chair)