Ternary nucleation of clusters containing water, sulfuric acid and ammonia may be a more favorable pathway for the formation of new atmospheric particles than binary nucleation without ammonia. We investigated the thermodynamics of clustering reactions with several ab initio and DFT methods. Studies of the formation of the binary clusters H₂O•NH₃, H₂SO₄•H₂O, and H₂SO₄•NH₃ show that the B3LYP/6-31G* method offers good accuracy, compared to limited experimental data and to higher levels of calculation, for relatively low computational cost. Preliminary results also show that the presence of ammonia does allow cluster growth to occur more favorably. Thermodynamic data to be presented shows that the addition of water to clusters is more favorable with ammonia present, as is the addition of sulfuric acid.