Space group describes an orthorhombic crystal with a body-centred lattice and the…
PHYSICS · Multi-part · Fermi University Physics · Mathematical Methods for Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction
Solid State Physics, Ch Symmetry and the classification of crystals
Problem
Space group Immm describes an orthorhombic crystal with a body-centred lattice and the full orthorhombic point-group symmetry mmm (three mutually perpendicular mirror planes) about each lattice point.
((a)) State what the leading I means for the lattice, and what each of the three m's means geometrically.
((b)) Starting from a general point (x,y,z), give the images produced by the three mirror operations and by the inversion centre their combination implies. How many distinct general positions does the point-group part of the symbol generate?
((c)) Add the centring translation and state the total number of general positions in the conventional cell.