Figure 1

Potential energy curves for (a) ${\mathrm{Ca}}^{+}({\mathrm{H}}_2{)}_4$ and (b) coronene-$\mathrm{Ca}({\mathrm{H}}_2{)}_4$ as a function of $\mathrm{Ca}\mathrm{\text{−}}{\mathrm{H}}_2$ distance $Z$. The coronene does not bind Ca at short $Z$ but binds via dispersion interactions at $Z\approx 4.0\AA$. The reference energy is taken to be at $Z=6.0\AA$. The MP2(FC) denotes aggressive frozen-core approximation where the Ca core orbitals are frozen up to $3p$ leaving only two valence electrons left to be correlated. Using the latter FC definition, the correlation energy for $\mathrm{C}{\mathrm{a}}^{+}$ is of course zero. For MP2 calculations of the coronene system, the PBE geometry was used.Reuse & Permissions