Microsolvation of lithium in ammonia: Dissociation energies and spectroscopic parameters of small Li(NH3)n clusters (n = 1 and 2) and their cations

Ab initio calculations on the alkali-solvent clusters LiNH3 and Li(NH3)2 and their cationic equivalents are reported. The calculations have been carried at various levels of theory, the highest being single-point CCSD(T) calculations with an aug-cc-pVQZ basis set, with the aim of establishing accurate Li-N bond dissociation energies of these clusters for the first time. Equilibrium structures and harmonic vibrational frequencies are also presented along with ionization energies for the neutral clusters. The results obtained should be of assistance in experimental studies of lithium-ammonia clusters and will provide important benchmark data for ab initio calculations on larger alkali-ammonia clusters.