CEM 913
Fall 2005
FUNDAMENTALS OF X-RAY CRYSTALLOGRAPHY
Instructor: Mercouri G. Kanatzidis
Final Exam Schedule December 14, 15
SYLLABUS
PURPOSE: This course will cover the basics of crystallographic science. We will start from symmetry, space-groups and the reciprocal lattice concept and end up with solution of crystal structures from diffraction data. Techniques that are used routinely such as Patterson interpretation, direct methods, Fourier synthesis, Difference Fourier synthesis and model refinement will be reviewed. Single crystal and powder diffraction techniques will also be covered. The goal of this course is to provide the student with an elevated theoretical understanding of how atoms and molecules are found in crystal space from diffraction data. This should help those who solve crystal structures using canned programs to understand what they are actually doing and hopefully help them use the programs more effectively. We will not cover how particular diffractometers work or how to use commercially available crystallographic programs.
TEXTBOOKS: (1) Structure Determination by X-ray Crystallography, by Ladd and Palmer
(2) X-ray Structure Determination, by Stout and Jensen
Other recommended Books
CLASS HOURS: Tuesday and Thursday, 10:20 - 11:40 am Room 136.
Assignments: Problem sets (~6-8)
Exams: There will be three exams Exam 1 October 6 (in class) Exam 2 November 17 (in class) Exam 3: Final exam, December 2
Useful Links
Interactive Tutorial about Diffraction
Course Contents
Crystal Geometry The crystalline state Symmetry , The Stereographic Projection. Miller indices 2- and 3-dimensional Point Groups Lattices Space Groups
International Tables for X-Ray Crystallography, Volume I Reciprocal Lattice X-rays origin, properties, safety X-ray diffraction and Bragg's Law (nl = 2d sinq) Ewald sphere X-ray diffraction techniques Single Crystal techniques Laue, Oscillation, Weissenberg and Precession Methods Fourier transforms Scattering of X-rays by crystals The atomic structure factor The structure factor x-ray diffraction electron diffraction neutron diffraction Friedel's law Systematic absences Practical determination of space groups
Structure of K6Yb3(PS4)5
Data reduction Lorenz-polarization Interpretation of intensity data Theory of structure factors and Fourier Synthesis The phase problem
Structure Determination Techniques The Patterson Method Direct Methods (intensisty statistics) Search methods Twinning
Twin-Refinement with SHELXL
Structure refinement Estimated standard deviations and the R value Derived Results
Powder Diffraction The Debye Scherrer method Strategies in Structure Determination from Powder Data Structure solution from powder data,
PDF analysis, The Rietveld Method
PbS crystals (galena)
The final exam will be based on oral presentations. Each student will be assigned a crystallographic topic for development and presentation to the class audience. A short paper (5-6-single spaced pages) on the assigned subject will be due. This is a chance for the class to expand upon a topic that I mentioned or covered only superficially in class. Here the students become teachers. You will get the chance to sharpen your skills in presenting your topics to non-specialists.
Examples of Topics
1. Incommensurate Crystal Structures 2. Structures from powders using Synchrotron Radiation 3. Structures from powders using Neutron Radiation 4. Direct Methods structure solution in SHELXS 5. PDF Analysis and diffuse scattering
6. Quasicrystallography 7. Twinning and the solution of twinned crystal structures 8. The use of Search methods in structure solution (examples)
9. X-ray Anomalous Scattering and its applications
10. Other (proposal from students to develop a topic encouraged)
11. Maximum Entropy method etc