LAUSR

Adsorption of the TaSi16 cluster on highly oriented pyrolytic graphite (HOPG) is studied using density functional methods. These calculations resolve some of the issues raised by the recent experiments of Shubita et al. (Shibuta, M.; Ohta, T.; Nakaya, M.; Tsunoyama, H.; Eguchi, T.; Nakajima, A. Chemical Characterization of an Alkali-Like Superatom Consisting of a Ta-Encapsulating Si16 Cage. J. Am. Chem. Soc. 2015, 137, 14015−14018) and provide additional insights into the system. For the first time, the ground-state structure of TaSi16 is obtained through a global search employing an evolutionary algorithm. A symmetric structure of the Si cage, together with a small charge transfer from Ta to the Si atoms, explains the observed core-level photoemission spectra. The ground-state isomer is deposited on HOPG at different points and in different random orientations. The cluster is found to be physisorbed on HOPG and retains the Ta-encapsulating cage structure, with little charge transfer between the cluster a...