(color online) Shear strain field maps of ε_xy calculated over the nano-single crystal specimen (Fig. 1(a)) at three different strain levels respectively: (a) , (b) , (c) . The color bar represents the variation of the shear strain, the positive value means counterclockwise rotation of the lattice and the negative value represents the opposite rotation. (d) The curves of shear strain ε (ε_xx, ε_yy, response to the external applied strain (, ε is obtained by averaging the strains of all the atoms across the sample. The inset shows the enlarged images of the region enclosed in the red shadow box.