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Page 6 of 10 Lu et al. Microstructures 2023;3:2023033 https://dx.doi.org/10.20517/microstructures.2023.28

Figure 4. Lattice profiles and strain maps of kink-kink configurations with different system sizes and wall-wall distance d. (A-D) Lattice
profiles for the bottom surfaces, top surfaces, lower walls and upper walls of samples with d = 10 l.u., 82 l.u. and 200 l.u. Strain maps in
(E) are colour-coded according to the atomic-level normal strain: ɛ with a wall-wall distance of d = 200 l.u. The sample sizes for (A-D)
xx
are 301 l.u. × 300 l.u., 501 l.u. × 500 l.u., 701 l.u. × 700 l.u., 901 l.u. × 900 l.u., 1,001 l.u. × 1,000 l.u., 1,201 l.u. × 1,200 l.u., 1,401 l.u. ×
1,400 l.u., and 1,601 l.u. × 1,600 l.u. The black lines indicate the bottom surface, lower wall, upper wall, and top surface.

maps [Figure 4E] are analysed. Strong strain deformations observed near the surfaces of small-sized sample
[Figure 4E(a-c)] decay when the system size increases [Figure 4E(d-f)] and almost disappear when the size
is over 1,400 l.u [Figure 4E(g and h)]. The simulated energies as a function of the wall-wall distances are
power laws for all thicknesses. They do not represent superpositions of two power laws of more complex
functions, which could have represented the intermediate range between the surface-dominated and bulk-
dominated interactions. The evolution of this size-dependent surface strain is, thus, seen as the change of
exponents of the wall-wall interaction in Figure 3B. The top layers bend nearly parabolically in opposite
directions so that the negative displacement of the bottom layer [Figure 4A] is the same as the positive
bending of the top layer [Figure 4B]. Small samples bend very strongly, while thick samples are more rigid.
The lower and upper domain walls show more local deformations at the kink positions. The same thickness