Equilibrate structure of the copper nano-wire models. The diameter of the nano-wires from left to right is 2 nm, 2.5 nm, 3 nm, 6 nm, and 10 nm, respectively. The green atoms are FCC structure atoms and the blue atoms are unidentified structure atoms.
(a) The spacing between NN atoms and (b) the stress in z direction (σzz) of atoms in various radial location along ⟨110⟩ direction of nano-wires. The inset in (b) is the potential energy of individual atoms. The black dash lines indicate the corresponding property of bulk copper.
Illustration of the contraction ratio versus diameter response in the nano-wires. The inset illustrates the proportion of surface atoms versus diameter. The filled squares are the calculated values, and the red line is the fitted curve.
The calculated stress-strain curve of copper nano-wires with different diameters. The inset plots the slope of stress-strain curves, which represents the instantaneous elastic modulus of copper nano-wires.
Snapshots of stacking fault nucleation at yield point; (a) front view, and (b) cross-sectional view during tension; (c) front view, and (d) cross-sectional view during compression. The green atoms are FCC structure atoms and the blue atoms are unidentified structure atoms. The red atoms are HCP structure atoms representing the formation of stacking fault.
Average atomic level potential energy of (a) surface atoms, (b) sub-surface atoms, and (c) internal atoms along ⟨110⟩ directions of various copper nano-wires during tensile and compressive load.
Average atomic level stress-strain curve for atoms from (a) surface layer, (b) sub-surface layer, and (c) internal layers on ⟨110⟩ directions of various copper nano-wires during tensile and compressive load.
Volume change ratio versus strain of various copper nano-wires. The inset shows volume change ratio of nano-wire with 6.0 nm diameter (blue line) and the predicted curve obtained by a constant Poisson's ratio 0.34 (brown line).
Calculated Poisson's ratio of various copper nano-wires as a function of strain.
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