Figure 1

Adsorption structures of the Alq${}_3$ meridional ($\mathrm{mer}$) and facial ($\mathrm{fac}$) isomers. In both “up” configurations [(a) and (c)] Mg atoms are lifted out of the surface plane because of strong O–Mg chemical bonds, whereas the surface is flat for physisorbed “down” configurations [(b) and (d)]. Arrows penetrating Al atoms indicate the orientation of the permanent dipole ($\mathcal{p}$) of the molecules. For simplicity, H atoms are removed from quinoline ligands.Reuse & Permissions

Figure 2

Decomposition of adsorption energy $E_{\mathrm{ad}}$ of the adsorption configurations within vdW-DF (black solid lines) and PBE (gray solid lines). A positive energy means an attractive interaction. In the “up” configurations [(a) and (c)], the adsorbate-substrate interaction $E_b$(mol-sub) gives a dominant binding, and the lateral intermolecular interaction $E_b$(mol-mol) has an additional contribution to stabilizing the adsorption especially when van der Waals interactions are included. However, the distortion energy of adsorbate and substrate $E_{\mathrm{relax}}$ substantially decreases $E_{\mathrm{ad}}$. PBE adsorption energies are very small even for the chemisorbed adsorbate.Reuse & Permissions

Figure 3

Spatial distribution of the nonlocal vdW correlation contribution to the molecule-substrate interaction [$\Delta f_{\text{NL}}(\mathbf{r}$)] (Ref. 35) of the Alq${}_3$/Mg(001) ($\mathrm{mer}$/up configuration). Top and side views of the isosurfaces which correspond to the attractive correlation contribution with values ranging from 2.1 (dark) to 0.7 (bright) $\times$ 10${}^4$ kJ mol${}^{-1}$ nm${}^{-3}$. The contribution is widely distributed between the top surface layer and the quinoline ligands adjacent to the surface. The largest contributions located at the O and Mg atoms show the chemical bond formation described within vdW-DF: the functional describes physisorption and chemisorption in a seamless fashion.[6] The attractive contribution by the PBE correlation (right panels) illustrates the O–Mg bond formation. Al, Mg, O, C, N, C, and H atoms are shown by white medium, white large, dark-gray (red in color) medium, black medium, gray (green) medium, and white small spheres, respectively.Reuse & Permissions