A Report

To continue the line of previous meetings with the same topic which were held in 1990 and 1997, the 36. international school of crystallography and ASI was again devoted to the tremendous progresses in electron crystallography. The course took place at the renown Ettore Majorana Centre for Scientific Culture in Erice, Sicily in June 2004 and brought together 87 participants from 32 different countries.
The very well received concept of the school was a moderate mixture of lectures given by leading experts in their field, live demonstrations of modern electron crystallography software, hands-on computer labs and many possibilities for open discussions. The first lectures of the course were used to work out a common basis to compensate for the different scientific background of the participants which came from biology, chemistry, crystallography, physics and materials science. This was achieved by talks on the fundamentals of crystallography (space group symmetry, crystallographic phase problem) and about the basics of modern transmission electron microscopy (instrumentation, image formation etc.).
As the course went on, the participants were stepwise introduced to the main topic which included also the latest and most advanced developments in electron microscopy for characterising the atomic structure and local chemistry of materials. How to apply these new methods in practise was throughout the course demonstrated by several examples ranging from technological important oxides, complex alloys and precipitates, over organic thin-films, natural occurring minerals, zeolites and other finely dispersed catalysts. Needless to stress the point that many of these materials frequently exist only as thin-films or nanocrystalline powders which can only be thoroughly studied by electron microscopy.
A full listing of the topics treated during the course is given in the following: space group determination from electron diffraction (ED) electron diffraction (SAED, nano-diffraction, CBED) kinematical and dynamical theory of ED quantification of electron data from images, diffraction patterns of nanocrystalline powders, single crystals and textures structure determination from ED using direct and Patterson methods maximum entropy and likelihood methods as an alternative for structure determination with ED data retrieval of the crystal potential from high-resolution electron microscopy images using crystallographic image processing and through-focus reconstruction of the exit wave function kinematical and dynamical structure refinement with ED data structure validation by quantum mechanical simulation methods high-resolution transmission electron microscopy and high-resolution scanning TEM (Z-contrast imaging) for structure determination non-common (new) instrumentation for electron crystallography (electron diffractometry, precession technique, gas-phase electron diffraction, Cs corrected field-emission TEM additional techniques like energy dispersive X-ray spectroscopy, electron energy loss spectroscopy and TEM sample preparation. Since the hands-on computer labs often required to turn the new background knowledge into practise this part turned out as an excellent check for the success of the lectures. Moreover, the hands-on labs provided a good forum to discuss problem related questions in small groups. A discussion forum on a larger scale were the held student corners, which allowed to discuss hot-topics and questions brought up by the students. Another very efficient event which intensified discussion and exchange of know-how between lecturers and participants was the lively poster session.
In retrospective one can say that this 10 days course on electron crystallography came extremely well-timed since we are now at an important turning point in the field. Whereas the scientific community one or two decades ago was still extremely sceptical about the reliability of structural results derived from electron data, the numerous examples of high-quality structures determined during the past years (almost all presented during the school) have turned electron crystallography into a widely accepted method aside the traditional methods for structure determination like X-ray and neutron diffraction. Another very important point are the new developments in instrumentation and assisting computer software which will certainly boost the field in the next years. Thus the participants have been witness of the spectacular results obtained by the new developed ED precession technique, which gives for the first time hope to get full control over dynamical diffraction (presentation by S. Nicolopoulos) and have seen new developed exit-wave reconstruction software for direct imaging of the projected atomic structure (talks by C. Kübel, J. Spence, C. Kisielowski). These new techniques added to the already existing pool of electron crystallography methods have the potential to revolutionise the whole field in the comming years. Thus even that the 36th course of the international school of crystallography and ASI is just over, it can truly be said that this event will rank as one of the high-lights in this field for many years.
The material (video, handouts) of the school is available at http://erice2004.docking.org/ and a book which will contain the extended lecture notes and poster abstracts is in manuscript.

Main lectures/papers given

Titles (speaker)
Diversity amidst similarity: a multidisciplinary approach to phase relationships, solvates and polymorphs (Herbstein)
What is electron crystallography? (Zou)
Basics of image formation in the electron microscope (Spence)
Introduction to electron diffraction (Morniroli)
The phase-problem in crystallography (Weirich)
Structure determination from HREM by crystallographic image processing (Zou)
Electron diffraction structure analysis (EDSA) of thin polycrystalline films - Part 1 (Klechkovskaya)
Solving and refining crystal structures from electron diffraction data (Gilmore)
Structure refinement by taking dynamical diffraction into account (Jansen)
Symmetry determination by electron diffraction (Morniroli)
Crystal structure determination by image deconvolution and resolution enhancement (Hua Jiang)
Electron diffraction structure analysis (EDSA) of thin polycrystalline films - Part 2 (Avilov)
Exploiting sub-Ångström abilities: what advantages do different TEM techniques offer? (Kisielowski)
Electron crystallography on beam sensitive materials - Part 1 (Tsuji)
Role of electron powder diffraction in solving structures (Labar)
Electron diffraction and diffractive imaging from organics (Spence)
Structure of zeolites determined by electron diffraction and high-resolution electron microscopy Part 1 (Terasaki)
Electron crystallography on polymorphs (Kolb)
Symmetry and structure (Hargittai)
New instrumentation for TEM ED structure analysis: ED combined with beam precession (Nicolopoulos)
Structure of zeolites determined by electron diffraction and high-resolution electron microscopy Part 2 (Terasaki)
Quantitative convergent beam electron diffraction (Zuo)
Electron crystallography on beam sensitive materials - Part 2 (Tsuji)
Electrons and X-rays compared: prospects for the future (Spence)
Analysis of local structure, chemistry and bonding by electron energy-loss spectroscopy, EELS (Mayer)
The effects of symmetry in real and reciprocal space (Hovmöller)
The maximum entropy method of solving crystal structures from ED data (Gilmore)
Electron diffraction structure analysis of thin polycrystalline films (Avilov)
Gas-phase electron diffraction for molecular structure determination (Hargittai)
Quasi-automatic solving and refining structures from selected area electron diffraction (Weirich)
Phase identification by combining local composition from EDX with information from diffraction database (Labar)
Electron crystallography in mineralogy and materials science (Nihtianova)
HRTEM investigation of nanocrystalline materials (Tonejc)
New insights into the nanoworld of functional materials (Cox)
3D reconstruction of inorganic crystals: theory and application (Zou)
Characterisation of catalysts by TEM (Wang)
Structure validation (Weirich)

Demonstration of software
D1 - Introduction to PROCESS DIFFRACTION (Labar)
D2 - The MSLS program (Jansen)
D3 - Introduction to CRISP (Zou)
D4 - Introduction to ELD / Direct Methods software (Zou)
D5 - The TRUE-IMAGE package (Kübel)
D6 - Introduction to TEXPAT (Oleynikov)
D7 - Introduction to the ELECTRON DIFFRACTION program (Morniroli)
D8 - Simulation of EM Images and diffraction patterns (Zuo)
D9 - Visual computing in electron crystallography, VEC (Jiang)
D10 - The CERIUS2 / MATERIALS STUDIO packages (Kolb)
D11 - Evaluation of EEL Spectra (Mayer)
D12 - The Moscow electron diffractomety programs (Avilov)

Hands-on computer labs
L1 - Process Diffraction (Labar)
L2 - MSLS (Jansen)
L3 - CRISP-1 (Zou, Oleynikov, Weirich)
L4 - ELD (Zou, Oleynikov, Weirich)
L5 - EM simulation (Zuo)
L6 - TEXPAT (Oleynikov)
L7 - CRISP-2 (Zou, Oleynikov, Weirich)