van der Waals dispersion power laws for cleavage, exfoliation and stretching in multiscale, layered systems

Abstract

Layered and nanotubular systems that are metallic or graphitic are known to exhibit unusual dispersive van der Waals vdW power laws under some circumstances. In this Brief Report we investigate the vdW power laws of bulk and finite layered systems and their interactions with other layered systems and atoms in the electromagnetically nonretarded case. The investigation reveals substantial difference between "cleavage" and "exfoliation" of graphite and metals where cleavage obeys a C2D-2 vdW power law while exfoliation obeys a C3 log D/D0 D-3 law for graphitics and a C5/2D-5/2 law for layered metals. This leads to questions of relevance in the interpretation of experimental results for these systems which have previously assumed more trivial differences. Furthermore we gather further insight into the effect of scale on the vdW power laws of systems that simultaneously exhibit macroscopic and nanoscopic dimensions. We show that, for metallic and graphitic layered systems, the known "unusual" power laws can be reduced to standard or near standard power laws when the effective scale of one or more dimension is changed. This allows better identification of the systems for which the commonly employed "sum of C6D-6" type vdW methods might be valid such as layered bulk to layered bulk and layered bulk to atom.