Binding and interlayer force in the near-contact region of two graphite slabs: Experiment and theory
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Via a novel experiment,Liu et al. [Phys. Rev. B85, 205418 (2012)] estimated the graphite binding energy, specifically the cleavage energy, an important physical property of bulk graphite. We re-examine the data analysis and note that within the standard Lennard-Jones model employed, there are difficulties in achieving internal consistency in the reproduction of the graphite elastic properties. By employing similar models which guarantee consistency with the elastic constant, we find a wide range of model dependent binding energy values from the same experimental data. We attribute some of the difficulties in the determination of the binding energy to: (i) limited theoretical understanding of the van der Waals dispersion of graphite cleavage, (ii) the mis-match between the strong bending stiffness of the graphite-SiO2 cantilever and the weak asymptotic inter-layer forces that are integrated over to produce the binding energy. We find, however, that the data do support determination of a maximum inter-layer force that is relatively model independent. We conclude that the peak force per unit area is 1.1 ᠰ.15 GPa for cleavage, and occurs at an inter-layer spacing of 0.377 ᠰ.013 nm.
The Journal of Chemical Physics
© 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in 139, 224704 (2013) and may be found at dx.doi.org/10.1063/1.4839615.
Surfaces and Structural Properties of Condensed Matter
Condensed Matter Modelling and Density Functional Theory