Abstract
The basal plane cleavage energy (CE) of graphite is a key material parameter for understanding many of the unusual properties of graphite, graphene and carbon nanotubes. Nonetheless, a wide range of values for the CE has been reported and no consensus has yet emerged. Here we report the first direct, accurate experimental measurement of the CE of graphite using a novel method based on the self-retraction phenomenon in graphite. The measured value, 0.37±0.01 J m−2 for the incommensurate state of bicrystal graphite, is nearly invariant with respect to temperature (22 °C≤T≤198 °C) and bicrystal twist angle, and insensitive to impurities from the atmosphere. The CE for the ideal ABAB graphite stacking, 0.39±0.02 J m−2, is calculated based on a combination of the measured CE and a theoretical calculation. These experimental measurements are also ideal for use in evaluating the efficacy of competing theoretical approaches.
Highlights
The basal plane cleavage energy (CE) of graphite is a key material parameter for understanding many of the unusual properties of graphite, graphene and carbon nanotubes
The interlayer binding energy is a relatively simple measure of the interlayer interactions and is defined as the energy per layer per area required separating graphite into individual graphene sheets. This energy is nearly equivalent to the exfoliation energy and is approximately equal to the cleavage energy (CE, the energy to separate a crystal into two parts along a basal plane) and twice the basal plane surface energy
In the Methods part, we describe how the generalized stacking fault energy (GSFE) is obtained based on accurate first-principles calculations and provide all of the functions and parameters used as input to the anisotropic Peierls– Nabarro grain boundary (APNGB) model applied to (0001) twist grain boundaries in graphite
Summary
The basal plane cleavage energy (CE) of graphite is a key material parameter for understanding many of the unusual properties of graphite, graphene and carbon nanotubes. Compared with the extremely strong sp[2] intralayer bonds, the interlayer interactions are controlled by much weaker van der Waals bonding This contrast leads to many novel physical and mechanical properties of graphite, such as maximal values of the electric and thermal conductivities, in-plane elastic stiffness and strength[2,4,5,6,7,8,9], and the minimum shear-to-tensile stiffness ratio[10]. The interlayer binding energy is a relatively simple measure of the interlayer interactions and is defined as the energy per layer per area required separating graphite into individual graphene sheets (for example, by uniformly expanding the lattice in the direction perpendicular to the basal plane) This energy is nearly equivalent to the exfoliation energy and is approximately equal to the cleavage energy (CE, the energy to separate a crystal into two parts along a basal plane) and twice the basal plane surface energy. The method we adopted is based on the recently discovered self-retraction phenomenon in graphite[29]
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