Deformation Behavior and Its Effect on the Mechanical Properties of Nanoparticles in Pure Nanoparticle-Modulated System

Abstract

Nanoparticles (NPs) are widely used in many practical applications. However, their deformation behaviors and the subsequent effects on their mechanical properties in pure nanoparticle-modulated systems still remain unclear. These research challenges were systematically investigated using coarse-grained molecular dynamics simulations. Firstly, it was observed that both the stiffness and tensile strength of the NPs system were greatly influenced by the cohesion energy of the NPs under uniaxial tensile/compressive loads. It was also revealed that the larger the cohesion energy between neighboring particles, the stronger the stiffness and strength. Secondly, the distribution and evolution of the local virial stress component, σ_xx of the NPs system with varying ε_p of the NPs under tension and compression were also explored. Finally, the effect of particle size on the mechanical properties and deformation mode of the NPs system were discussed. These results have certain reference value for the optimal design of pure nanoparticle-modulated system materials.

Appendices

Appendix: Simulation Codes

Relax.iN.

Tension.in.

Attachment

According to the generalization of the virial theorem, the average virial stress at a volume, Ω_i, around particle, I, at position, r_i, can be expressed as follows (Ref 21).

$$ \sigma^{i} = \frac{1}{{\Omega_{i} }}\left( { - m\frac{{{\text{d}}{\varvec{u}}_{i} }}{{{\text{d}}t}} \otimes \frac{{{\text{d}}{\varvec{u}}_{i} }}{{{\text{d}}t}} + \frac{1}{2}\sum\limits_{{j\left( { \ne i} \right)}} {{\varvec{r}}_{ij} \otimes {\varvec{f}}_{ij} } } \right) $$

where m is the mass of a particle in the numerical sample, and u_i is the relative displacement of i for the reference position. Hence, the material time derivative of u_i is the thermal excitation velocity of the particle. The interparticle force, f_ij, applied on particle i by particle j is:

$$ {\varvec{f}}_{ij} = \frac{{\partial \Phi_{ij} }}{{\partial {\varvec{r}}_{ij} }}\frac{{{\varvec{r}}_{ij} }}{{\left\| {{\varvec{r}}_{ij} } \right\|}}\;{\text{with}}\;{\varvec{r}}_{ij} = {\varvec{r}}_{i} - {\varvec{r}}_{j} $$

where Φ_ij is the total energy of the coarse-grain ensemble, including the bead-spring and rotational-spring and pairwise interatomic potentials, as previously described.