Binding energies and structures of C+Arn (n=1–5), clusters from first principles

We report the minimum energy geometries, binding energies and vibrational spectra of the C+Arn (n=1–5), clusters which were recently recorded in a time-of-flight mass spectrometer. The C+Ar3 cluster has a planar structure with two long and one short C–Ar bonds while the C+Ar4 cluster forms a square of D4h symmetry with the carbon atom in the center. The observed drop in the incremental binding energy for the successive Ar atom addition from n=2 to n=3 and from n=4 to n=5 justifies the classification of the n=2 and 4 as magic number clusters in the experimental mass spectrum.