The lattices of twin and parent are symmetrically oriented across a symmetry plane called the twinning plane.
Twins form as the result of the shear-stress component of an applied stress which is parallel to the twinning plane and lies in the twinning direction n1.
This diagram assumed that the twin interface is exactly parallel to the twinning plane K1.
A twin boundary that parallels the twinning plane is said to be a coherent boundary.
Whenever possible, twins will try to grow in such a manner as to develop straight sides parallel to the twinning plane, K1.
Since the formation of the twinned substructure requires that the twinning plane is situated parallel to the growth found, the crystal growth in the crystallographic directions other than <111> leads to almost complete disappearance of the twinned substructure.
According to the micro-diffraction pattern, the twinning planes of the condensates are normal to the direction of crystal growth, i.
The secondary Manebach twin can be formed at the point where the crystal is broken in the (001) twinning plane.
It also has four symmetry planes that are parallel to the fourfold axis, yet it has no (001) Manebach twinning plane.
Twinned crystals with a (0001) twinning plane are very common.
This is clearly visible on the striated Manebach twin faces whose junctions make a visible twinning suture along their (010) twinning planes.
The angles between the (111) twinning planes
(arccos (1/3) [approximately equal to] 70.