A fully molecular dynamics-based method for modeling nanoporous gold

Abstract

Models that can be used to describe nanoporous gold are often generated either by phase-field or Monte-Carlo methods. It is not ascertained that these models are closely matching experimental systems, and there is a need for other variants. Here is proposed an original approach to generate alternative models, which is solely based on molecular dynamics simulations. Structures obtained with this method are structurally characterized by determining the ligaments diameter distributions, the scaled genus densities and the interfacial shape distributions. Selected mechanical characterizations are also done by deforming the structures in tension and in compression. Structural and mechanical properties are in good agreement with experimental and theoretical published results.

Molecular Dynamics Simulations of Deformation Mechanisms in the Mechanical Response of Nanoporous Gold

“…Although various attempts have been carried out to understand the mechanical behaviour of np Au for bio-molecular detection and energy conversion applications, bicontinuous morphologies as a combination of circular and elliptical pore shapes have been studies so far focusing on the relative density and pore size [10,11,21,[23][24][25][26][27]30,31,35,37,40,41]. This work demonstrates, for the first time, the pore shape effect in the mechanical behaviour of np Au through determining the stress transfer mechanism between ligaments.…”

“…The porous media is modelled through considering different pore shapes, including circle, horizontal ellipse (H-ellipse), vertical ellipse (V-ellipse), square and hexagon with a same relative density of 0.343 and an average ligament size of 5 nm. These geometrical parameters are selected based on an average design studied previously through a series of computational [11,35] and experimental [10,27,29] works. The relative density, ρ = ρ p ρ B , stands for the ratio of the density of the porous structure, ρ p , to the density of the bulk material, ρ B .…”

“…Figure 2 shows the stress-strain curves for various pore shapes with ρ = 0.343 and an average ligament size of 5 nm. Both ρ and the ligament size are based on the already published data from computational [11,35] and experimental [10,27,29] studies. The change in stress is linear until the tensile yield stress, σ T Y , while the stress changes non-linearly afterwards to the ultimate tensile stress, σ T U .…”

“…The theory of surface elasticity [33], a unit-cell micromechanical model [13] and finite element methods [34] have been developed to implement the surface effect on the mechanical behaviour of np structures. Molecular dynamics (MD) simulations, on the other hand, are considered as a powerful approach to study the mechanical properties of np Au [11,[35][36][37][38][39][40][41]. While plastic deformation and defect formation are the main focus of atomic simulations in np structures [37][38][39]41], the surface effect on the asymmetric mechanical behaviour is studied in order to modify the scaling law for np Au [11,40].…”

“…The ligament size and pore density have so far been the focus of studies to understand the mechanical behaviour of np Au with bicontinuous pore shapes [11,35,[37][38][39][40][41][42], while a recent study demonstrated a significant pore shape effect on the mechanical behaviour of np silicon [17]. Moreover, the force transfer mechanism between ligaments is a fundamental aspect of np Au in general, especially for sensing applications [8,19].…”