Adsorption of Ar on graphite using London dispersion forces corrected Kohn-Sham density functional theory

Using Kohn-Sham (KS) density functional theory, the adsorption of Ar on graphite has been computed with various conventional exchange-correlation functionals. While the local density approximation yields a reasonable estimate of equilibrium distance and energy, three generalized gradient approximated functionals fail. Extending the KS Hamiltonian by an empirical nonlocal and atom-centered potential enables quantitative predictions. The adsorption on the on-top, hollow, and bridge sites has been investigated, and it is found that the London dispersion corrected calculations prefer the hollow site which is in agreement with other studies. Furthermore, the adsorption effect of several submonolayer coverages and of the graphitic bulk has been studied.

Figure 1

(Color online) Sketch of four triclinic unit cells of $1∕32$ coverage of Ar on the hollow site on graphite. The interatomic Ar–Ar distance corresponds to four graphite lattice constants $\left(9.824\mathrm{\AA }\right)$.

Figure 2

KS DFT results for argon–graphite adsorption, $E^{\mathrm{Ad}}$ as a function of distance $d$. Left hand panel: $1∕32$ coverage adsorption curves for hollow sites from several exchange-correlation functionals, DCACP corresponds to $\mathrm{DCACP}+\mathrm{BLYP}$. Middle panel: $1∕32$ coverage adsorption energies for the hole, bridge, and on-top sites using the $\mathrm{DCACP}+\mathrm{BLYP}$ functional. Right hand panel: adsorption energies of $1∕32$, $1∕16$, and $1∕8$ coverage using the $\mathrm{DCACP}+\mathrm{BLYP}$ functional. $1∕16$ a) corresponds to the interatomic distance of two graphite lattice constants $\left(4.912\mathrm{\AA }\right)$, and $1∕16$ b) to $\sqrt{3}$ graphite lattice constants $\left(4.254\mathrm{\AA }\right)$.