Modes of vibration of the hexagonal close-packed lattice
The modes of vibration of the hexagonal close-packed structure is worked out on the basis of the Raman theory of crystal vibrations. The character tables are drawn up, and the vibrations are derived by a method due to E. V. Chelam without using the character table of the space-group. It is found that there are 13 vibrations with degeneracies 1, 2, 2, 4, 3, 3, 3, 3, 3, 3, 6, 6, 6. The planes which take part in each mode and the directions of vibration for these are also described.