A density functional theory study of the hydrates of NH3•H2SO4 and its implications for the formation of new atmospheric particles

Density functional molecular orbital theory was used at the B3LYP/6-311++G(2d,2p)//B3LYP/6-311++G-(2d,2p) level of theory to study the hydrates of NH3. H2SO4. nH(2)O for n = 0-5 and NH3.(H2SO4)(2). H2O Neutrals of the first four NH3. H2SO4. nH(2)O clusters (n = 0-4) spontaneously formed and were determined to be hydrogen-bonded molecular complexes of H2SO4, H2O, and NH3. Double ions (clusters containing a NH4+ cation and a HSO4- anion) spontaneously formed in clusters of NH3. H2SO4. nH(2)O where n = 1-5. The energetics of the hydration and isomerization reactions also were calculated. Double ions are not energetically favorable until NH3. H2SO4. 4H(2)O. The free energy of formation from free NH3 and H2SO4. nH(2)O had a maximum at n = 3 at room temperature with Delta G approximate to -3 kcal/mol. NH3.(H2SO4)(2). H2O was studied to see if NH3 can; initiate new atmospheric particle growth. It has been shown that NH3 has no role in the initialization of new atmospheric particles.