Fracture mechanics of multi-layer molybdenum disulfide

Nguyen

Proc. Natl. Acad. Sci. U.S.A.

et al. 2022

Quantifying the intrinsic mechanical properties of two-dimensional (2D) materials is essential to predict the long-term reliability of materials and systems in emerging applications ranging from energy to health to next-generation sensors and electronics. Currently, measurements of fracture toughness and identification of associated atomistic mechanisms remain challenging. Herein, we report an integrated experimental–computational framework in which in-situ high-resolution transmission electron microscopy (HRTEM) measurements of the intrinsic fracture energy of monolayer MoS 2 and MoSe 2 are in good agreement with atomistic model predictions based on an accurately parameterized interatomic potential. Changes in crystalline structures at the crack tip and crack edges, as observed in in-situ HRTEM crack extension tests, are properly predicted. Such a good agreement is the result of including large deformation pathways and phase transitions in the parameterization of the inter-atomic potential. The established framework emerges as a robust approach to determine the predictive capabilities of molecular dynamics models employed in the screening of 2D materials, in the spirit of the materials genome initiative. Moreover, it enables device-level predictions with superior accuracy (e.g., fatigue lifetime predictions of electro- and opto-electronic nanodevices).

Section: Discussionmentioning

confidence: 99%

Atomistic measurement and modeling of intrinsic fracture toughness of two-dimensional materials

Nguyen

Proc. Natl. Acad. Sci. U.S.A.

et al. 2022

“…In this paper, we use molecular dynamic modeling to study the fracture properties of polycrystalline graphene when hydrogenation is confined to the grain boundaries. Considering the difficulties of conducting experiments at nanoscale, molecular dynamic modeling provides an invaluable tool to study phenomena occurring at short time and length scales. ,− By conducting molecular dynamics on both precracked and pristine polycrystalline graphene sheets, we investigate the effect of hydrogenation on both the mechanical and fracture properties of graphene sheets. The impact of polycrystalline grain size is also studied by considering polycrystalline sheets with different average grain sizes.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Fracture Properties of Polycrystalline Graphene with Hydrogenated Grain Boundaries

Elapolu

Tabarraei

2021

J. Phys. Chem. C

Self Cite

Molecular dynamics (MD) is employed to study the mechanical and fracture properties of polycrystalline graphene with hydrogenated grain boundaries. Polycrystalline graphene sheets with an average grain size of 4, 6, and 8 nm are considered. The impact of hydrogenation percentage on the mechanical strength and fracture toughness of polycrystalline graphene sheets is investigated. Polycrystalline graphene with and without an initial crack are considered. The results show that due to the hydrogenation the strength of polycrystalline graphene sheets reduces. The impact of hydrogenation is significantly greater on the strength of polycrystalline graphene without an initial crack. The strength of polycrystalline graphene sheets with hydrogenated grain boundaries decreases with increase in temperature. The impact of temperature on the strength increases with increase in hydrogenation percentage at the grain boundaries. The results also show that the hydrogenation of the polycrystalline graphene affects the crack propagation path. As the hydrogenation percentage of grain boundaries increases, the crack path changes from intragranular to intergranular. Furthermore, the increase in the hydrogenation reduces the critical stress intensity factor of polycrystalline graphene. Such changes in the strength, fracture toughness, and crack path are due to the hydrogen embrittlement of grain boundaries which reduces their fracture energy.

“…Atomistic simulations have become a valuable tool in studying properties of nanomaterials. − More recently, atomistic scale modeling of crack propagation is used for the extraction of traction–separation laws of cohesive zone. Yamakov et al used molecular dynamics simulations to derive the traction–separation law of intergranular fracture of aluminum.…”

Section: Introductionmentioning

confidence: 99%

Atomistic Simulation-Based Cohesive Zone Law of Hydrogenated Grain Boundaries of Graphene

Elapolu

Tabarraei

2020

J. Phys. Chem. C

Self Cite

The impact of hydrogenation on the fracture toughness and strength of grain boundaries in graphene are studied. Molecular dynamics (MD) modeling is used to extract the traction−separation laws of two high-angle symmetric grain boundaries. The MD modelings are conducted on two bicrystalline graphene sheets, while their grain boundaries are hydrogenated. The impacts of the adsorption site of the hydrogen atom, hydrogenation percentage, and temperature are studied. The results show that in general the hydrogenation of the grain boundaries leads to a reduction in both their strength and ductility. The adsorption site is an important factor for determining the level of the impact of hydrogenation on the fracture properties of the grain boundary. An increase in the temperature from 1 to 300 K reduces the strength of hydrogenated grain boundaries, whereas toughness increases initially and then decreases.