Relationships between the elastic and fracture properties of boronitrene and molybdenum disulfide and those of graphene

Abstract

A consistent set of 2D elastic and fracture properties of hexagonal boron nitride (h-BN) monolayers (boronitrene) and molybdenum disulfide (MoS) nanosheets is derived. Reported literature values for Young's moduli and fracture strengths, based on experiments and DFT calculations, were used to estimate the line or edge energy with a local 2D bond-breaking model. Consistent information was obtained for intrinsic fracture properties. The basic mechanical properties of boronitrene are roughly 25% lower than the corresponding graphene values. This is consistent with the tensile bond force model, and the lower ionic-covalent bonding energy of sp-hybridized B-N bonds in comparison with sp-hybridized carbon bonds. While the intrinsic stiffness and strength of MoS correlate with the strength of its constituent chemical bonds, DFT calculations of the line or edge energy scale with roughly two times the Mo-S bonding energy, whereas the 2D bond-breaking model yields a correlation similar to that found for h-BN. Additional failure properties such as the fracture toughness and strain energy release rate were determined. Together with the intrinsic strengths a Griffith plot of the effective strength of defective h-BN and MoS versus the square root of half the defect size of single defects such as (multi)vacancies and micro-cracks exhibits a slope similar to that of the graphene plot.

Multiscale framework for simulation-guided growth of 2D materials

“…At the atomic scale, first-principles calculations have shown that the anisotropic edge energies are critical to the island morphology evolution of MoS 2 10 and h-BN. 11 The Reactive Force Field (ReaxFF) Method 12 has been applied to revealing the chemical reaction mechanisms and pathways of forming the 2D materials from the gas/powder precursors, [13][14][15] and predicting the growth morphologies of a few islands. The kinetic Monte Carlo (KMC) method has also been coupled with first-principles calculations to predict the island growth morphology as a function of flux and precursor stoichiometry.…”

Prediction of mechanical properties of 2D solids with related bonding configuration

“…A detailed discussion of the fracture toughness of graphene has been provided recently. 4,10 Its mean value of K IC ¼ 1.1 Â 10 À3 N m À1/2 is used here for calibration of the strength ratios. Table 3 displays the toughnesses of the other group members obtained with the ratios of the fracture strengths.…”

Failure in Two-Dimensional Materials: Defect Sensitivity and Failure Criteria

“…Other hexagonal graphene-like 2D materials, including boronitrene [98], phosphorene [91], and silicene [11,99] containing preexisting cracks, behave in a similar way under a tensile load. These single-layer materials fail in a brittle way, and their failure is governed by the strength of the atomic bonds at the crack tip.…”

“…These single-layer materials fail in a brittle way, and their failure is governed by the strength of the atomic bonds at the crack tip. Similar to graphene, the ZZ direction is the preferable direction of crack propagation in these materials, which indicates that the bonds in the AC direction have the stronger capability to resist crack propagation than the ZZ direction [21,78,[98][99][100].…”