Quantitative prediction of the fracture toughness of amorphous carbon from atomic-scale simulations

Abstract

Fracture is the ultimate source of failure of amorphous carbon (a-C) films, however it is challenging to measure fracture properties of a-C from nano-indentation tests and results of reported experiments are not consistent. Here, we use atomic-scale simulations to make quantitative and mechanistic predictions on fracture of a-C. Systematic large-scale K-field controlled atomic-scale simulations of crack propagation are performed for a-C samples with densities of $\rho =2.5,3.0\text{ and }3.5{\text{g/cm}}^3$ created by liquid quenches for a range of quench rates ${\dot{T}}_q=10-1000\text{K/ps}$. The simulations show that the crack propagates by nucleation, growth, and coalescence of voids. Distances of $\approx 1\text{nm}$ between nucleated voids result in a brittle-like fracture toughness. We use a crack growth criterion proposed by Drugan, Rice \& Sham to estimate steady-state fracture toughness based on our short crack-length fracture simulations. Fracture toughness values of $2.4-6.0\text{MPa}\sqrt{\text{m}}$ for initiation and $3-10\text{MPa}\sqrt{\text{m}}$ for the steady-state crack growth are within the experimentally reported range. These findings demonstrate that atomic-scale simulations can provide quantitatively predictive results even for fracture of materials with a ductile crack propagation mechanism.

9 pages, 5 figures, 3 tables, to be submitted to Physical Review Materials Journal

References in corpus (2)

• Machine learning driven simulated deposition of carbon films: from low-density to diamondlike amorphous carbon
• Insights into the fracture mechanisms and strength of amorphous and nanocomposite carbon

Cited by in corpus (3)

• Interatomic potentials: Achievements and challenges
• Thermal transport of amorphous carbon and boron-nitride monolayers
• Structure and mechanical properties of monolayer amorphous carbon and boron nitride