1.56: H centered cell
The H centered cell ( triple hexagonal cell ) is an alternative description of the hexagonal Bravais lattice . From the conventional hP cell one obtains the hH cell by taking the new basis vectors by means of one of the following transformation matrices, which give three possible orientations of the hH cell with respect to the hP cell:
H 1 : 110/-120/001 H 2 : 2-10/110/001 H 3 : 1-20/2-10/001
The resulting hH cell has centering nodes at 1/3,2/3,0 and 2/3,1/3,0.
Secondary and tertiary elements in the hP cell are exchanged in the hH cell. For
example , the space-group symbol P 3 m 1 become H 31 m when the triple cell is used.