Chemistry

DIFFRACTOMETRIC CHEMICAL STRUCTURISTICS (A.Y. 2022-23) The crystalline state Simple ionic solids, with molecular ions, neutral molecular, covalent solids, metallic solids. Symmetry in crystals: definition of element and symmetry operation; proper and improper operations. Punctual symmetry. The case of the five flat lattices. Translational symmetry: translation lattice, unit cell; the seven crystal systems; Bravais lattices; Senone's law; Bravais law; definition of lattice plane and Miller indices; helicopter axes and glide planes; the equation zonal; point symmetry of crystal lattices: crystal classes; space groups: asymmetric unit; representation of space groups; notation in use in the International Crystallography Tables; examples of some common space groups in low symmetry systems. Single crystal X-ray diffraction Single crystal growth techniques. Choice of sample. Use of the polarized light microscope. X-ray sources conventional and unconventional: X-ray tubes, synchrotron radiation. X-ray emission spectra. Absorption of X-rays. X-ray detection techniques. The single crystal and powder diffractometer. Diffraction reminders of the light. Theory of the interaction of X-rays with matter: scattering (coherent and incoherent) from an atomic electron, from an atom, from a molecule, from a crystal. Laue equations. Bragg diffraction. The reciprocal lattice. Reflection sphere of Ewald and limit sphere. The intensity of the diffracted wave. Integrated intensity and its measurement. Friedel's law. The diffusion anomalous. Periodic functions and Fourier series in complex and trigonometric form; The structure factor. The factor of temperature. Primary and secondary extinction of X-rays. Fourier synthesis and the phase problem. The reciprocal lattice as a consequence of the Fourier series developability of the point functions of the crystal lattice; Fourier synthesis of the electron density of a crystal: observed, calculated and difference. Effect of symmetry on diffraction intensity: systematic absences and spatial group determination. Determination of the absolute configuration. Main methods resolution of crystalline structures. The Patterson function: interatomic vectors, Patterson function in shape complex and trigonometric, symmetry of the Patterson function, deduction of atomic coordinates from the maxima of Patterson function, heavy atom method. SIR and MIR. direct methods. Refinement of crystalline structures: the least squares method. Constraints and restraints. Disagreement index. Weighing scheme. Accuracy of parameters structural obtained with X-ray diffraction; effect of thermal motion on bond distances. X-X technique. Examples of applications of X-ray diffraction to the determination of the structure of inorganic, organic and organometallic compounds. X-ray powder diffraction The powder method: general information, applications and limits. The powder diffractometer. Factors influencing the shape of diffraction peaks. Rietveld method. Neutron diffraction from powders and single crystals Properties of neutrons. Neutron sources and detectors. Characteristics and main applications of neutron diffraction. X-N technique. Study of the electron density distribution. Crystalline engineering Definition of crystal engineering through the use of intermolecular interactions. Synton concept; structures conditioned by the formation of hydrogen and halogen bonds. Guide to using the CSD database

Knowledge of the fundamentals of the Physics II course (Electromagnetism, Waves, Optics)

Basic texts recommended and available in the library: C. Hammond:”The Basics of Crystallography and Diffraction” 3rd ed. (2009). C. Giacovazzo (Ed.): "Fundamentals of Crystallography". IUCr OUP 2nd ed. (2002). Slides and articles provided by professors.

not mandatory

At the end of the course there is an oral test

il corso si compone di 48 ore di lezioni frontali

Knowledge of the fundamentals of the Physics II course (Electromagnetism, Waves, Optics)

C. Hammond:”The Basics of Crystallography and Diffraction” 3rd ed. (2009). C. Giacovazzo (Ed.):"Fundamentals of Crystallography". IUCr OUP 2nd ed. (2002). teaching material and articles provided by teachers.

the attendance of the lessons is not mandatory

Oral examination

The course consists of 48 hours of frontal lessons