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Wednesday 29th August
Opening Lecture: Powder Diffraction: State of the Art and Perspectives
Lecturer: Gilberto Artioli (University of Padova, Italy)
Current powder diffraction instruments, methods and acquired protocols will be briefly reviewed. Their role as standardized tools for the investigation of solid matter will be discussed, with a view on recent instrumental and methodological developments. It is argued that (1) presently powder diffraction is often used well below its potential for providing key information on materials, (2) the combination or the simultaneous use of powder diffraction with spectroscopic and/or imaging techniques are assuming an increasingly important experimental role in the investigation of matter. Examples will be discussed, drawn from different fields of research such as cultural heritage materials, industrial applications, and advanced characterization techniques.
Fundamental Aspects of Powder Diffraction I
Lecturer: Ernesto Mesto (University of Bari, Italy)
X-ray powder diffraction (XRPD) is a powerful non-destructive technique for characterizing crystalline materials. It provides qualitative and quantitative phases analysis, and information on crystal structure, texture, grain size, crystallinity, strain, and crystal defects. The students will be introduced to the basic theoretical aspects (interaction of X-rays with crystalline solids, principles of diffraction, scattering of periodic arrays, etc.) and to the experimental details of the powder X-ray diffraction (Debye-Scherrer and Bragg-Brentano geometry). The aim is to provide a basic knowledge of diffraction methods for the polycrystalline materials analysis.
Fundamental Aspects of Powder Diffraction II: Preliminary data treatment
Lecturer: Gennaro Ventruti (University of Bari, Italy)
Powder diffraction data consist of a raw file of scattered intensity as a function of scan angle. This raw diffraction file contains abundant information for various applications. To accurately interpret and analyse patterns some data treatment processes are required. For example, when applications involve the identification of phases in a specimen it is necessary to extract a reduced pattern which lists integrated intensities and positions of distinguishable reflections to be used in searching and matching routine. The obtained reduced pattern may be also used in indexing, lattice parameters refinement and ab initio structure solution. This lecture aims to drive the user through the different steps employed in the treatment of raw powder diffraction data (background subtraction, data smoothing, Kα2 stripping, peak searching, data extraction) and obtain preliminary information.
Modern Powder Diffraction Instruments
Lecturer: Andy Fitch (ESRF, Grenoble, France)
Powder diffraction measurements can be carried out using a laboratory X-ray source, or at a central facility exploiting synchrotron radiation or neutrons. Whereas laboratory sources are the most accessible, and are the basis for most powder diffraction measurements made in the academic, industrial and analytical domains, synchrotron radiation and neutrons allow the design of specialised instruments, with very high d-spacing resolution, high time resolution, and allowing measurements using hard X-ray energies. The talk will give an overview of the current possibilities.
Qualitative analysis: the PDF 4+ database
Lecturer: Matteo Leoni (University of Trento, Italy)
Working with real data: let’s avoid to reinvent the wheel! Why you need a database? What can you find in PDF4+? What’s the idea behind a search match.
Tutorial Session: QUALX2.0
Lecturer: Aurelia Falcicchio (Institute of Crystallography-CNR, Italy)
QUALX2.0 is a computing program freely distributed for qualitative phase analysis by X-ray powder diffraction data. The software is based on the traditional search–match method, it is able to manage the commercial database PDF-2 maintained by ICDD, and a freely available database POW_COD generated by the structure information contained in the Crystallography Open Database. QUALX2.0 demonstration will be devoted to present examples of applications by using standard and non-standard computational and graphic options of the program.
Thursday 30th August
Powder Diffraction for Solving Crystal Structures
Lecturer: Elena Kabova (University of Reading, UK)
Powder X-ray diffraction (PXRD) is widely used in industry for solid form screening but can we routinely and confidently employ it for crystal structure solution? This talk aims to answer the above question by giving a broad overview of the last 20 years of successfully employing powder X-ray diffraction as a crystal structure determination tool. In particular, I will aim to cover the wide range of strategies used to overcome the limitations of PXRD data and highlight the challenges in solving increasingly complex molecular crystal structures from PXRD alone.
Indexing and Space Group Determination
Lecturer: Anna Moliterni (Institute of Crystallography-CNR, Italy)
The correct determination of the unit cell parameters and the space group is a fundamental task for the success of the structure solution process. Both indexing and space group identification are usually trivial in case of single crystal data; in case of powder diffraction data, they can be challenging steps due to typical and often concomitant problems (i.e., overlap of reflections, wrong background description, preferred orientation effects, …).
The main approaches aimed at finding unit cell parameters and space group will be described, with particular attention to the methods implemented in the EXPO program. Some examples of applications of EXPO to experimental data will be given.
Structure Solution in Reciprocal Space
Lecturer: Rosanna Rizzi (Institute of Crystallography-CNR, Italy)
The reciprocal space (RS) methods for crystal structure solution from powder diffraction data work in the reciprocal space applying the following scheme: first, the structure factor moduli