Configuration interaction calculations on the cyclic carbon clusters C8, C10, Pt@C8 and Pt@C10 and their anionic forms

Ab initio single plus double excitations configuration interaction calculations in the context of relativistic effective core potentials are reported for C8, C10, Pt@C8 and Pt@C10 clusters in their neutral and ionic forms. The predicted geometries of cyclic C 8 2 - and C 10 2 - correctly justify double coincidence mass spectra results as compared to linear C 8 2 - and C 10 2 - . The effects of Pt encapsulation in these clusters are discussed in terms of binding energies and equilibrium geometries. The Pt@C8 and Pt@C10 clusters have binding energies of 1662 kJ/mol and 2200 kJ/mol, respectively. Binding energies for Pt encapsulation are only favorable for the doubly charged carbon clusters, indicating that stable Pt encapsulation only occurs for the C 8 2 - and C 10 2 - clusters.