Table 1.

Parameters calculated from literature X-ray crystallography structures for armchair and zig-zag twin boundaries in graphite, hBN and MoSe₂

	Graphite				hBN		MoSe2
Direction of twin boundary	ac		zz		ac	zz	ac	zz
Slip direction	zz		ac		zz	ac	zz	ac
L slip	α	α / √ 3	2α / √ 3	3α / √ 3	α	3α / √ 3	α	3α / √ 3
c (nm)	0.67	0.67	0.67	0.67	0.67	0.67	1.23	1.23
a (nm)	0.25	0.25	0.25	0.25	0.25	0.25	0.33	0.33
Lslip (nm)	0.25	0.14	0.29	0.43	0.25	0.43	0.33	0.56
θt(°)	40.3	23.9	46.0	64.9	41.2	65.9	30.0	48.6

Higher order twin zz angles in graphite (2α/√3 and 3α/√3) are likely to be less favourable due to the ease of splitting of such basal dislocations into separate partial dislocations with lower energy