Bending modes, elastic constants and mechanical stability of graphitic systems

TL;DR

This study uses advanced density functional calculations to comprehensively determine the elastic constants and exfoliation energies of graphitic systems, revealing how stacking misorientations influence mechanical properties and exfoliation ease.

Contribution

It provides the first complete set of elastic constants and exfoliation energies for various stacking configurations in graphitic systems using state-of-the-art methods.

Findings

Stacking misorientations significantly lower C44 by at least an order of magnitude.

Random stacking flakes are easier to exfoliate due to lower exfoliation energy and C44.

Turbostratic graphitic systems exhibit ultralow friction behavior.

Abstract

The thermodynamic and mechanical properties of graphitic systems are strongly dependent on the shear elastic constant C44. Using state-of-the-art density functional calculations, we provide the first complete determination of their elastic constants and exfoliation energies. We show that stacking misorientations lead to a severe lowering of C44 of at least one order of magnitude. The lower exfoliation energy and the lower C44 (more bending modes) suggest that flakes with random stacking should be easier to exfoliate than the ones with perfect or rhombohedral stacking. We also predict ultralow friction behaviour in turbostratic graphitic systems.