Interlayer cohesive energy of graphite from thermal desorption of polyaromatic hydrocarbons

Abstract

We have studied the interaction of polyaromatic hydrocarbons ͑PAHs͒ with the basal plane of graphite using thermal desorption spectroscopy. Desorption kinetics of benzene, naphthalene, coronene, and ovalene at submonolayer coverages yield activation energies of 0.50 eV, 0.85 eV, 1.40 eV, and 2.1 eV, respectively. Benzene and naphthalene follow simple first order desorption kinetics while coronene and ovalene exhibit fractional order kinetics owing to the stability of two-dimensional adsorbate islands up to the desorption temperature. Preexponential frequency factors are found to be in the range 10 14 -10 21 s Ϫ1 as obtained from both FalconerMadix ͑isothermal desorption͒ analysis and Antoine's fit to vapor pressure data. The resulting binding energy per carbon atom of the PAH is 52Ϯ5 meV and can be identified with the interlayer cohesive energy of graphite. The resulting cleavage energy of graphite is 61Ϯ5 meV/atom, which is considerably larger than previously reported experimental values.

Ab-<i>initio</i> studies of adsorbate-surface interactions

“…[3][4][5] The short bond lenghts resulting from the intralayer binding are well described by density functional theory (DFT) 18,19 in the Perdew-Burke-Erzerhof (PBE) 69 generalized-gradient approximation (GGA) 68 for the exchange-correlation (XC) functional. The binding between layers is governed by nonlocal long-range dispersion forces, 3 which are poorly described by DFT within local 20 or semilocal XC functionals.…”

“…There are a few exceptions, however. For instance, upon adsorption the ECN's for Ni 5 and Pt 4 rise roughly 12 % and 19 %, i.e., from 3.19 NNN and 2.49 NNN to 3.57 NNN and 2.97 NNN, respectively. As these examples show, the cluster-graphene interaction tends to enhance the average coordination.…”

“…101,102 For example, QMC calculations by Spanu et al 103 have yielded E b = −56 meV/atom for graphite AB, close to the experimental value reported by Zacharia et al (52 meV/atom). 5 RPA-based methods can be combined with DFT computations to exploit the translational symmetry of the system. A good example is the study by Lèbegue et al, 102 which found E b = −48 meV/atom and comparably accurate elastic constants.…”

“…Tais medidas diferem em mais ide 40% umas da outra. [3][4][5][6][7] Isso mostra que nossa compreensão sobre a natureza desse material ainda é bastante pobre. A interação entre pequenos grupos de metais de transição com uma folha de grapheno é outro exemplo em que nosso conhecimento é limitado.…”

“…29,30 The are many measurements and simulations for geometric and electronic properties that have yielded results that differ by more than 40%. [3][4][5][6][7] Many of thse properties depends on the curvature of the interlayer binding energy curve. Thus, to improve our understanding of the bulk properties of graphite, we are going to investigate the shape of the curvature of the interlayer binding energy in the DFT scope, taking into account the vdW corrections.…”