1 Department of Chemistry and Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West, Montréal, Québec H4B 1R6, Canada.

A polarizable potential model for M(+)-NH3 interactions (M(+) = Li(+), Na(+), K(+), Rb(+), Cs(+)) is optimized based on the ab initio properties of the ion-ammonia dimers calculated at the MP2 level of theory. The optimized model reproduces the ab initio binding energies of M(+)(NH3)n (n = 2-4) and M(+)(NH3)n(H2O)m (n, m = 1-3 and n + m = 4) clusters and gives relative solvation free energies in liquid ammonia in good agreement with experimental data, without further adjustments. It also...