STRUCTURE AND PROPERTIES OF NE-N(-IN-MOLECULES APPROACH() CLUSTERS FROM A DIATOMICS)

The diatomics-in-molecules (DIM) approach is used to investigate the s tructure and properties of Ne-n(+) clusters for 3 less than or equal t o n less than or equal to 25. The DIM energies and wavefunctions can b e obtained within the representation matrix formalism without the appe arance of overlap integrals, and antisymmetry for permutation of elect rons between different atoms can also be taken into account implicitly . The results are formally the same as those obtained in the tradition al DIM framework. Candidate structures for the lowest energy minimum a t each size are located using a basin-hopping technique, and the relat ive stabilities appear to agree well with intensity anomalies in the m ass spectra of Ne cluster cations. Significant differences in the equi librium configurations of Ne-n(+) compared Ar-n(+) appear for n > 3, c orresponding to the relatively flexible ionic core undergoing a transi tion at n = 15 from symmetric tetraatomic to asymmetric triatomic, wit h the closely spaced diatomic unit preserved in both structures. The i nduced dipole-induced dipole interaction is found to affect the global minimum structure and electronic transition intensities significantly . Electronic spectra for Ne-n(+) and associated ionization potentials for neutral Ne-n clusters are predicted. The excitation spectra are fo und to be dominated by a visible band, resembling the major transition in symmetric Ne-3(+) and determined by the charge transfer from the c entral diatom to the wing atom(s) of the core. An ultraviolet band, or iginating from the transition within the diatom, is predicted to be th e next most intense even at the equilibrium configuration, in contrast to heavier ran gases.