Geometrical structure and stability of buckminsterfullerene complexes containing mono- and poly-atomic molecules

Structure vis-à-vis the stability of mono- and poly-atomic buckminsterfullerene (C\(_{60}\)) complexes are capable of providing intrigue information about these systems. To obtain an insight of these complexes, geometrical parameters of fullerene encapsulated noble gas elements (He, Ne and Ar) and poly-atomic molecules (H\(_2\), H\(_2\)O, NH\(_3\) and CH\(_4\)) are computed at the restricted Hartree-Fock (RHF) as well as density functional (DFT) at the Becke, 3-parameter, Lee-Yang-Parr (B3LYP) level of theories. Ellipticity values estimated from mean maximal and mean minimal diameters of these endohedrals are found to be \(\sim\)0.2 which indicate that these complexes are of spheroidal shape. It is further observed that the fullerene ring is resilient to deformation and the structural parameters of these systems depend more on the method than the embedded system. Binding energies of these complexes are computed at the RHF, DFT, second order Möller-Plesset perturbation (MP2), spin-component scaled (SCS) MP2 and coupled-cluster with single and double excitation (CCSD) level of theories to assess electron correlation effects on the stability of these endohedrals. Resulted energies from the RHF procedure are found to be positive (energetically unstable), whereas those yielded by MP2 and SCS-MP2 procedures predict these endohedrals to be stable. CCSD calculations also exhibit similar trend except for H\(_2\)O complex. Binding energies obtained using RHF, MP2, SCS-MP2 and CCSD procedures with correlation consistent polarized basis indicate a strong correlation between the basis set and the stability of these endohedral complexes.