Shape Effect of Surface Defects on Nanohardness by Quasicontinuum Method 
Z. Zhang, C. Wang, X. Hu and Y. Ni
Micromachines, 11, 909 (2020).

ABSTRACT
Nanoindentation on a platinum thin film with surface defects in a rectangular
shape and triangular shape was simulated using the quasicontinuum method to
study the shape effect of surface defects on nanohardness. The results show that
the nanohardness of thin film with triangular defects is basically larger than
those with rectangular defects, which is closely related to the height of the
surface defects at the boundary near to the indenter. Moreover, the triangular
defect might have an enhancement effect on nanohardness by a certain size of the
defects and the boundary orientation of the defect, where such an enhancement
effect increases as the defect grows. Furthermore, the nanohardness decreases
when the defect is folded from wide to narrow in the same atom cavity, and
particularly expresses a more obvious drop when the height of the defects
increases. In addition, larger sizes of the rectangular defect induce more
reduction in nanohardness, while the nanohardness of the triangular surface
defect is sensitive to the periodic arrangement of atoms changed by the boundary
orientation of the defect, which is well explained and demonstrated by the
calculation formula theory of necessary load for dislocation emission.