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MSc Crystallography
Advanced Symmetry
Aims & Objectives
The overall aim of this MSc module is to explain the salient points of
higher-symmetry space groups,
namely those belonging to the tetragonal, trigonal, hexagonal, and
cubic crystal systems.
The objectives of each lecture are given below:
- Lecture 1
To explain the solution to symmetry problems set for the vacation;
To revise the basic principles involved for orthorhombic space groups;
To give students confidence in deriving space group information from
single-crystal diffraction data.
- Lecture 2
To illustrate the additional symmetry elements present in centred orthorhombic
space groups;
To discuss the concept of extended space-group symbols;
To teach the students how to deduce space-group symmetry
from diffraction data of a crystal possessing a centred lattice;
To introduce the concept of d-glide planes with reference to space groups
Fdd2 and Fddd.
- Lecture 3
To develop the concepts involved in tetragonal space groups belonging
to the Laue class 4/m;
To briefly survey the higher-symmetry tetragonal space groups
belonging to the Laue class 4/mmm;
To show how the two Laue classes may be distinguished in a diffraction
experiment;
To introduce the concept of enantiomorphic pairs of space groups.
- Lecture 4
To develop the concepts involved in cubic symmetry;
To discuss the differences between the two cubic Laue classes
m-3 and m-3m.
- Lecture 5
To introduce the concept of trigonal symmetry and the diamond-shaped unit
cell associated with it;
To introduce the symmetry operators resulting from threefold symmetry;
To introduce the concept of the reciprocal-space coordinates hkil;
To develop the concepts involved with the Laue classes
-3m1 and -31m and
to demonstrate the relationship between them;
To show how the different Laue classes may be distinguished in a diffraction
experiment;
To introduce the concept of rhombohedral symmetry and the relationship
between the R-centred hexagonal and primitive rhombohedral unit cells;
To relate the rhombohedral and cubic unit cells.
- Lecture 6
To extend the concepts of trigonal symmetry to hexagonal space groups;
To show additional uses for hkil indices in hexagonal systems;
To discuss the differences between the two hexagonal Laue classes
6/m and 6/mmm.
- Lecture 7
To revise space-group symmetry from low to high symmetry;
To illustrate sub-group and super-group relationships;
To very briefly discuss the concept of higher-symmetry systems;
To illustrate the latter with colour symmetry and magnetic spin.
Links to
MSc Course Aims & Objectives
and
Advanced Symmetry
Timetable 1996/7.