|SCIENTIFIC DISCIPLINARY SECTOR||CHIM/02|
The course is devoted to the diffraction techniques for the study of crystalline materials.
At the end of the course students are expected to have acquired the knowledge on the theoretical principles of diffraction; to know the main experimental techniques and their possible use; to be able to understand and interpret the diffraction data, to solve simple crystallographic problems.
The course aims at using the theoretical concepts of diffraction to analyze and interpret diffraction data (both on powders and single crystals) from a practical point of view. At the end of the lessons the student will be able to correctly interpret and use the International Tables of Crystallography, and will have acquired useful knowledge for the characterization of crystalline materials. In particular, the student is expected to be able to interpret structural data, to analyse simple powder diffraction patterns, identifying the phases present through indexing and calculation of the lattice parameters. In addition the student should be able to set a structural refinement on single crystal data, and on powder data using the Rietveld method.
The course will be done in a traditional way, with lectures and exercises. The lectures will be interspersed with exercises and examples carried out with the contribution of all students.
In addition, topics will be identified among those not directly addressed in class but closely related to the contents of the course, as possible subjects for further study by the students. In this case, the deepening and further study (both individual and in small groups) will be completed in a session of presentation and discussion, which will be shared by the whole class.
Usually, the practical experiences are activities carried out by means of a computer; they take place in the classroom for groups of students
- Elements of elementary crystallography: symmetry elements, crystal lattices, point groups, space groups. Planes and crystallographic directions. Description and use of the International Tables of Crystallography.
- Diffraction theory : Nature and production of the RX. Safety and practical considerations. X-ray diffraction and neutron/electron diffraction (notes). Scattering factor and structure factor. Bragg's law, reciprocal lattice, Ewald sphere.
- Experimental techniques: Diffraction from polycrystalline samples and single crystals. Sample preparation and data collection strategies. Use of crystallographic databases.
Resolution and structural refinement: The intensity of the diffraction peaks. The electron density. The phase problem. Solution methods: synthesis of Patterson, direct methods.
Practical exercises: Identification of the phases present in a polycrystalline sample; structural refinement with the Rietveld method; structural resolution "ab initio" using of intensity 'data from single crystal and / or powders.
Besides the material available on Aulaweb, the following textbooks are recommanded:
A. Immirzi, C. Tedesco, “La diffrazione dei cristalli” 2a Edizione. Cooperativa Universitaria Athena
C. Giacovazzo, H.L. Monaco, G. Artioli, D. Viterbo, G. Ferraris, G. Gilli, G. Zanotti, M. Catti “Fundamentals of Crystallography” Ed. C. Giacovazzo
M.F.C. Ladd, “Symmetry in molecules and crystals”
G.H.Stout, L.H.Jensen, “X-ray structure determination”, Macmillan Publishing Co, N.Y (1968)
V. K. Pecharsky, P. Y. Zavalij, “Fundamentals of powder diffraction and structural characterization of materials”
Kluwer Academic Press
Tabelle Internazionali di Cristallografia Vol.1-4
Office hours: Students can contact the teacher at any time by e-mail in order to make an appointment for any problem / information regarding the course
From 28 February 2023 (see https://chimica.unige.it/didattica/orari_SC )
All class schedules are posted on the EasyAcademy portal.
Students can choose two different methods of examination: 1) traditional oral exam on various topics covered during the course. Usually three questions, one of which is on the theoretical part, one on experimental techniques, one on aspects concerning the interpretation and analysis of structural data. 2) An in-depth essay on a topic of crystallography, previously agreed. For the latter method both a written report and an oral presentation are required. The oral examination is always conducted by two faculty members and on average has a duration of at least 40 minutes; the commission will thus be able to verify wether the educational objectives are reached or not . When these are not met, the student is invited to deepen the study and to use further explanations by the teacher
Both the reasoning capacity of the student and his skill in solving simple theoretical problems are evaluated. The examination should ascertain whether the student has acquired the theoretical concepts of diffraction, and if it is able to apply them to simple real examples