A benchmark for layer cohesion energetics in graphitic systems, via the Random Phase Approximation
John F. Dobson, Griffith University, Australie
e-mail:J.Dobson@griffith.edu.au
Mardi 15 décembre 2009, 15h00
Systems and nanostructures built on graphene layers are important in various
emerging technologies. The cohesion of graphitic layers occurs primarily via
dispersion forces. It has recently been shown analytically that these forces
have an unusual asymptotic behaviour at large graphene layer separations D
(E ~ -D-3).
This behaviour is not captured by common theories that sum R-6
contributions, nor by theories of the "vdWaals" type. The dispersion energies
near the equilibrium layer spacing D=D0 are however not accessible
by purely analytic means, and their value in this regime has been
controversial for some years, with sparse and inconsistent experimental data
and no credible theoretical values. Because of the importance of graphitic
systems, a reliable benchmark is urgently needed, Here we report very recent
work using the Adiabatic Connection Fluctuation Dissipation Theorem within
the Direct Random Phase Approximation, carried through to numerical
convergence without further approximation. This has been applied to the
layer binding energy curve of graphite at all separations including near
to equilibrium. A benchmark binding energy is thus obtained. This will
be compared with very recent work via vdW-DF and Diffusion Monte Carlo methods.