Mechanical performance of (bi)metallic nanowires under tension and compression

One-dimensional nanostructures, such as nanowires (NW) and nanotubes (NT) are the focus of many studies due to their unique mechanical, electronic, and optical properties. In particular, NT and NW deformations has been experimentally and theoretically studied, resulting in different breaking mechanisms. Mono-crystalline structures (MC) has been the focus of these studies, giving a characteristic elastic regime followed by a sharp stress drop, associated with fast nucleation of defects. Additionally, there are nanowire synthesis methods that create poly-crystalline structures (PC), with multiple crystalline grains separated by grain-boundaries.

Our work presents the mechanical properties (Young modulus, fluence point, etc.) at different mono-metallic and bimetallic NW using molecular dynamic simulations with LAMMPS software. Embedded-atom method inter-atomic potentials were used, which correctly describe elastic properties of Ni, Fe, Cu, etc. 1; and allow simulations for large atomic structures, similar to experimental results.

For Ni structures, the stress-strain plot shows an elastic regime until the fluence point is reached, then follows a plastic regime ending in the fracture of the structure. These deformations are associated with different defects such as staking faults and twins. Also, different fracture mechanisms are compared between MC and PC structures. 2

Bimetallic FeNi PC nanowires show a plastic zone wider than their mono-metallic counterparts. These results envisaged the design of new materials with tailored mechanical properties.

We acknowledge the financial support of DICYT 041931BR project and "Fondo basal para centros cientficos y tecnolgicos" FB0807. J. Rojas-Nunez acknowledges the financial support of the CONICYT's "doctorado nacional" scholarship PCHA-21150699.

References:

1 Y. Mishin et al., Phys. Rev. B. 59, 3393 (1999).

2 J. Rojas-Nunez et al., Computational Materials Science, 168, 81 (2019).