Master degree in Materials Science

Structure characterization and modeling

Structure characterization and modeling

Academic year 2021/2022

Sommario del corso

• Course objectives
• Results of learning outcomes
• Course delivery
• Learning assessment methods
• Program
• Suggested textbooks and readings
• Teaching tools

Course objectives

The course aims at providing an overview on the most widespread characterization methods yielding, possibly with support from theory, detailed information on the structure of matter in all its forms: solids (crystalline and amorphous), liquid and gases, bulk and nanostructured materials. After reviewing the fundamentals of probe/matter interaction for the main structural probes (X-ray photons, neutrons, electrons) and the probe-specific advantages/limitations, the course deals with theoretical principles and main experimental geometries for structural determination by X-ray/neutron elastic scattering, as well as for local structural analysis by X-ray absorption spectroscopy. Key differences and complementarities between X-ray and neutron scattering are emphasized, to guide the students towards an effective exploitation of such probes for the characterization of materials. Modern large-scale facility-based X-ray (synchrotrons and XFELs) and neutron sources are also presented, illustrating how to exploit their properties to solve challenging structural problems. The course also aims at developing applied knowledge and know-how about theoretical modelling approaches, employed in synergy with scattering/spectroscopy techniques to guide, complement and strengthen the structural understanding of functional materials.

Results of learning outcomes

• Understanding theoretical bases and obtainable information for the principal structural characterization techniques based on X-ray/neutron elastic scattering and X-ray spectroscopy.
• Gaining knowledge on source properties and experimental setups for structural techniques applied at the laboratory and large-scale facility level.
• Developing the ability to select the most appropriate probe(s) and experimental technique(s) for structural determination of a given class of materials and/or to solve research questions connected with structural properties.
• Developing an integrated characterization/modelling approach, by learning how to choose and operatively build up the most appropriate structural model, how to simulate relevant observables, and how to interpret and present the results.

Course delivery

The course include frontal lessons (7 CFU) and a “hand-on” training module (1 CFU), all given in English.

Attendance in presence to the frontal lesson is warmly reccommended.

Alternatively, on-line streaming of the lesson is avaliable, connecting to the following links according to the course timetable for each of the professors of the course:

Prof. Elisa Borfecchia https://unito.webex.com/meet/elisa.borfecchia

Prof. Matteo Signorile https://unito.webex.com/meet/matteo.signorile

Prof. Alessandro Pavese https://unito.webex.com/meet/alessandro.pavese

Learning assessment methods

Oral examination, including theory and exercises.

Program

STRUCTURE CHARACTERIZATION

• Probes for structural characterization - photons, electrons and neutrons: basic properties; wavelength/energy requirements for atomic-scale characterization; probe-matter interaction: general scheme and probe-specific advantages/limitations.
• Structural determination by elastic scattering - X-rays and neutrons: elastic scattering processes and their formal representation; transition probability and momentum transfer vector; diffused signal intensity; atomic scattering power and neutron scattering length.
• Long-range ordered systems and disordered systems: translation invariance and related implications on intensity distribution; pair distribution function for disordered systems; structure refinement versus structure solution.
• Setups and experimental geometries for X-ray powder diffraction: transmission versus parafocussing instrumental geometries; resolution and role of elastically diffused X-ray detecting strategy.
• Large-scale facility-based X-ray sources and their impact on X-ray structural analysis: Review of X-ray tubes; synchrotron radiation - physical bases; structure of a synchrotron; principal properties; mention to X-ray Free Electron Lasers; key advantages to enable/facilitate XRD analysis of challenging systems; specialized methods: anomalous and time-resolved XRD.
• Neutron sources and nuclear/magnetic scattering methods: nuclear fission reactors and spallation sources; experimental setups and methods for neutron diffraction (detectors and monochromators, diffractometers; time-of-flight; neutron magnetic scattering); critical comparison with X-ray based techniques.
• Local structural determination by X-ray absorption spectroscopy (XAS): Basic principles of XAS - XANES and EXAFS regions; basic experimental setups; EXAFS qualitative/quantitative analysis and relevance of initial structural models.

STRUCTURE MODELLING

• Review of methods for the simulation of materials: overview on main simulation strategies; choice of the simulation method vs. size of the system.
• Choice of the structural model: from molecules to 3D; cluster vs. periodic approach.
• Simulation of observables: spectroscopies, diffraction, interaction energies; use of observables for method/structural model validation.
• Modelling to support structural assessment: examples of experimental data interpretation driven by modeling; spectroscopies augmented by simulation.
• Hands-on training sessions: handling with structural databases (ICSD, CCDC, COD); constructing structural models with molecular graphics tools; performing cluster and 3D calculations; results interpretation and critical comparison of the outcomes from different approaches.

• Lesson slides, corse notes and eventually video-recordings (sufficient to adequately prepare the exam).
• Additional textbooks and suggested further readings:

1. "Synchrotron Radiation: Basics, Methods and Applications"; S. Mobilio, F. Boscherini, C. Meneghini, Eds.; Springer, 2015.
2. "Neutron Scattering: A Primer"; R. Pynn; Los Alamos Science 19, 1990, www.fas.org/sgp/othergov/doe/lanl/pubs/number19.htm
3. E. Borfecchia, D. Gianolio, G. Agostini, S. Bordiga, C. Lamberti, “Characterization of MOFs. 2. Long and Local Range Order Structural Determination of MOFs by Combining EXAFS and Diffraction Techniques”, in: "Metal Organic Frameworks as Heterogeneous Catalysts"; F. X. Llabrés i Xamena and J. Gascón, Ed.; Royal Society of Chemistry, Cambridge, 2013, p. 143-208, Chapter 5.
4. Selected papers and reviews from the scientific litterature presented at lesson.

Class schedule

• Teaching materials
• Exams and finals
• Go to Moodle
• Visit the forums