Structures and relative stabilities of $$ \left[ {{\text{Mg}}\left( {{\text{NH}}_{3} } \right)_{n = 1 - 10} } \right]^{2 + } $$ MgNH3n=1-102+ clusters, obtained by using both M06-2X/6-31++G(d,p) and MP2/6-31++G(d,p) levels of theory, are reported in this paper. Binding energies and clustering energies are also given. Our computations indicate that clustering energies for the fourfold- and fivefold-coordinated systems with ammonia molecules in the second solvation shell are very close to the available experimental values. Calculated binding energies show that the + 2 charge influences even the ammonia molecule in the second coordination shell. Using a fitting procedure, we reached the convergence and the value of − 35.0 kcal/mol is suggested. Temperature effects on the isomeric distribution for each n size (in the range of 25–400 K) show that for n = 2–7, only the most stable isomers are present, while for n = 8–10 there is a competition between the most stable isomers that are quite close in energy.