This web page contains 15 lectures and handout notes given by Dr. Cora Lind for her Chem 4980/6850/8850: X-ray Crystallography course at the University of Toledo (Ohio). The preparation of these lectures was in part supported by National Science Foundation CAREER award DMR-0545517. Thanks to Prof. Lind and the University of Toledo Department of Chemistry for permission to post these videos and notes.
This lecture discusses what is a crystal, defines the concept of a unit cell and defines
the seven classes of unit cells. Growth of crystals is also discussed.
The sharp facets of crystals are determined by the underlying symmetry of the
unit cell; these facets are described by Miller indices.
Lecture 3 relates the unit cell to the concept of the lattice and introduces the 14
Bravais lattice types. Then point symmetry elements -- the symmetry that can be found in discrete objects are introduced.
Lecture 4 expands from symmetry of discrete objects to those of infinitely repeating
patterns that fill space. This requires additional types of symmetry elements. Symmetry
operations can be combined in a limited number of ways. For discrete objects there are
32 point groups, for infinite objects there are 230 space groups.
This talk provides an overview of space group symbols and then introduces how to
read a space group description in the International Tables of Crystallography, volume A.
The lecture ends with a description of sub- and super-group relationships.
This lecture introduces the concept of the reciprocal lattice and how to relate
this to the scattering from a crystal.
Lecture 7 (continued): Reciprocal Space, End & Exercises
Continuation of the previous lecture, with a brief review and then covering
the Ewald sphere concept, which allows one to visualize the geometry of
diffraction. The formulae for computing the d-space using real and reciprocal
lattice constants and ending with a contrast between single crystal and powder
diffraction. The 2nd half of the lecture Prof. Lind reviews symmetry with the class,
which may be of little value via video.
Structure factors provide both intensity and phases for the diffracted beams.
This presentation shows how the structure factor equation arises from the positions
of atoms in the unit cell. This equation is used to show how systematic absences occur,
where classes of reflections are required to have zero intensity by symmetry.
Refinement takes an approximate set of atomic coordinates and finds the optimum
model to fit the data. Least-squares minimization is introduced as a way to
optimize fits. The lecture also discusses how one uses the fit model to
This lecture introduces the method that Hugo Rietveld introduced for the
refinement of crystal structures from powder diffraction data, what sort of
data are best for this and some of the software available. How to find common
problems in fits from viewing patterns graphically is also shown.
The first part of this lecture explains that a synchrotron produces
very intense x-ray beams with a wide range of accessible energy.
This allows types of measurements that are not possible with lab-based equipment,
such as high pressure diffraction and x-ray spectroscopies. The differences between
neutron and x-ray scattering are presented, as well as some information about neutron