The weak point of the graphene material

In 2008, experiments were carried out at Columbia University that led to the receipt of pure graphene, a single layer of graphite with a thickness of a single atom, which has since become the strongest material known to mankind. This finding actually led to the question - how and why does graphene break?

In 2008, experiments were carried out at Columbia University that led to the receipt of pure graphene, a single layer of graphite with a thickness of a single atom, which has since become the strongest material known to mankind. This finding actually led to the question - how and why does graphene break?

Using quantum theory and supercomputers, researchers have been able to uncover the mechanisms leading to mechanical failure of pure graphene following tensile stress. In an article recently published in the scientific journal Physical Review Letters, the researchers showed that when graphene is exposed to equal stretching in all directions, it becomes a new structure that is mechanically unstable.

The researchers explain that this failure mechanism constitutes phonon instability in a soft form. A phonon is a common vibrational pattern of atoms within a crystal, similar to waves moving in a liquid. The fact that a phonon becomes "soft" under conditions of tensile stress means that the system can reduce its energy by deforming the atoms along the vibrational pattern and moving to a new crystalline arrangement. Under sufficient strain, graphene reaches a state where its honeycomb-like hexagonal arrangement is tilted toward disconnected hexagonal rings. This new crystal is structurally weaker, leading to mechanical failure of the graphene layer.

"Our findings are interesting in several respects," notes the researcher. "Soft forms of phonons were first identified in the sixties in the field of ferroelectric phase transition, but they were never directly attributed to the development of mechanical fracture. For the most part, defects in the material will always lead to premature failure, but the pure nature of graphene allows us to test our prediction. We have already planned a number of new interesting experiments in order to directly observe the results of the theoretical prediction of a soft form."

The lead researcher adds and explains that this is the first case ever that a soft optical phonon has been linked to a mechanical failure and therefore it is reasonable to assume that this innovative failure mechanism is not exclusive to graphene but may also be common in other thin materials. "As nanotechnology becomes increasingly common and widespread, understanding the nature of the mechanical behavior of two-dimensional systems, such as graphene, also becomes extremely important. We believe that stretching may be used as a tool to engineer the properties of graphene, and as a result, understanding its limits is essential."

The news about the study

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