In addition, the restriction of small twin spacing on dislocation dissociation also decreases the obstacles for the subsequent Barasertib cell line glide of dislocations in twin lamellas. The dislocation density is also an indicator of find more plastic deformation. The evolutions of dislocation densities versus compression depth are depicted in Figure 5. It is noted that for the compression of the twin-free nanosphere, the dislocation density maintains nearly a constant for δ/R > 13.3%

when the nucleation of dislocations is balanced by the dislocation exhaustion. While for the twinned nanospheres, the dislocation density increases gradually as compression progresses. Decreased twin spacing increases dislocation density, while continuous refinement of twin spacing below 1.88 nm does not improve dislocation density apparently. We also use the newer potential developed

MM-102 by Mishin et al. [32] to simulate the same problem, and quite similar deformation characteristics are observed. Figure 5 Evolution of dislocation density inside nanosphere with different twin spacing. Then we examine the influence of loading direction by fixing the TB spacing at 3.13 nm and changing the tilt angle θ from 0° to 90°. Figure 6 gives the corresponding load-compression depth relation. The reduced Young’s modulus in different loading directions is fitted by the Hertzian contact theory (Equation 2). Owing

to the local mechanical property under indenter varies as the loading direction changes, the reduced Young’s Protein kinase N1 modulus declines quickly from 287.4 to 141.4 GPa. As shown in Figure 6, when the twin tilt angle θ is larger than 10°, the averaged atom compactness in compression direction is close to that in <110 > direction; hence, all the fitted reduced elastic moduli are around 141.4 GPa, which is close to the theoretical prediction 148.7 GPa of bulk material in <110 > direction [27]. Figure 6 Load versus compression depth response of nanosphere with different twin tilt angle. In the plastic deformation regime, the load-compression depth curves tend to decline continuously as the tilt angle θ increases from 0° to 75°, while rise as the tilt angle θ increases further from 75° to 90°. Such dependence on loading direction also appears in the strain energy up to a given compression δ/R = 53.3%, as displayed in Figure 7. The variation of plastic deformation in different loading direction implies a possible switch of deformation mechanism in nanospheres. Figure 7 Strain energy of the deformed nanosphere as a function of twin tilt angle up to δ / R  = 53.3%. Figure 8 examines the atomic patterns inside three nanospheres with various loading directions. In all cases, dislocations will nucleate from the contact fringes, as shown in a1, b1, and c1 of Figure 8.