The adsorption and molecular orientation of Dy@Cs2 isomer I on Au（111） has been investigated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@Cs2 molecules tend to grow along the step edges of Au（111）, forming small clusters and molecular chains. Adsorption of Dy@Cs2 on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@Cs2 is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@Cs2 molecules in the islands prefer the adsorption configurations with the major C2 axis being approximately parallel to the surface of the substrate. Three preferable orientations of the Dy@Cs2 molecules are found in a two-dimensional hexagonal close packed overlayer. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.
By the first-principles calculations, most studies indicated that the （1102）-CoO2 termination of LaCoO3 cannot be stabilized, which disagrees with the experimental observation. Besides the crystal structure, we found that the spin states of Co3＋ ions could affect surface stability, which previously were not well considered. By examining the different states of Co3＋ ions in hexagonal-phase LaCoO3, including low spin, intermediate spin, and high spin states, the surface grand potentials of these facets are calculated and compared. The results show that the spin states of Co3＋ ions have an important influence on stability of the LaCoO3 facets. Different from the previous results, the stability diagrams demonstrate that the （1102）- CoO2 termination can stably exist under O-rich condition, which can get an agreement with the experimental ones. Furthermore, the surface oxygen vacancy formation energies （Eov） of stable facets are computed in different spin states. The Eov of these possible exposed terminations strongly depend on the spin state of Co3＋ ions： in particular, the Eov of the HS states is lower than that of other spin states. This indicates that one can tune the properties of LaCoO3 by directly tuning the spin states of Co3＋ ions.
