International
Tables for
Crystallography
Volume A
Space-group symmetry
Edited by M. I. Aroyo

International Tables for Crystallography (2015). Vol. A, ch. 1.5, p. 80

Figure 1.5.1.3 

H. Wondratscheka and M. I. Aroyob
[Figure 1.5.1.3]
Figure 1.5.1.3

Body-centred cell I with aI, bI, cI and a corresponding primitive cell P with aP, bP, cP. The origin for both cells is O. A cubic I cell with lattice constant [a_{c}] can be considered as a primitive rhombohedral cell with [a_{\rm rh} = a_{c} {1 \over 2} \sqrt{3}] and [\alpha = 109.47^{\circ}] (rhombohedral axes) or a triple hexagonal cell with [a_{\rm hex} = a_{c} \sqrt{2}] and [c_{\rm hex} = a_{c} {1 \over 2} \sqrt{3}] (hexagonal axes).