The atomic arrangement at a twin boundary in a face-centered cubic metal is shown in Fig.
Because atomic bonds are strained in these twin interfaces, they must possess higher interfacial energies than the {111} twin boundary of face-centered cubic metals.
A twin boundary that parallels the twinning plane is said to be a coherent boundary.
Chritian, Crystallography of Deformation Twin Boundary Movements in Indium-Thallium, Acta Metallurgica, 2, 101 (1954).
crystal and nucleation of defects including
twin boundary and dislocation during deformation have been researched extensively [9-12].
Formation of a {111}
twin boundary can enhance the SPE rate, especially on (111)-oriented seed.
Tilt twin disorder of the kind shown in Figure 4 maybe occurring, with the larger twin boundary sites more likely to contain the sodium ion.
If the dopant concentration is sufficiently high, then this twin boundary region will become the "bulk" and the rhombohedral "bulk" region will become the twin boundary, giving a continuous intensity shift from rhombohedral-like reflections to tetragonal-like reflections, as is experimentally observed.
This is because the resistance of the twin boundary movement and the energy which needs to overcome the resistance also increases with the increment of the twin boundary motion quantity during the movement of the twin boundary.
Because the movement of the martensite twin boundary depends on strongly temperature and the internal stress of the material, and temperature and the internal stress decide completely the energy barrier height, which need to overcome in the twin boundary movement, above the experiment result, the energy moving the twin boundary reflects the energy barrier height.
Obviously, at the same temperature, the magnetic field is applied along the crystal different directions, the difference of the energy for twin boundary moving and the twin boundary suffering the resistance is the importantly reason that the magnetic field-induced strain depends on temperature and the applied field direction.
An extreme case is a merohedral twin for which S = 1 in which the lattice is continuous through the
twin boundary. These twins occur in cases where the motif has less symmetry than the lattice; the twin is formed when the motif is rotated by a symmetry operation of the lattice but not of the motif.