The Study On The Thermodynamic Properties Of The Growth Of Ultrafine Aerosol Clusters In The Atmosphere

Observations indicate that there exists a strong correlation between the change of the intensity of galactic cosmic rays (GCR) and the climate of the Earth. The possible mechanism is that the galactic cosmic rays change the energy balance of atmosphere by influencing Earth’s cloudiness, which is attributed to the change of atmospheric composition concentration that prompt the formation of new aerosol particles. The understanding of the microscopic process how the ionization affects of GCRs changes the cloudiness is crucial to address whether GCR has influence on climate. By the combination of molecular dynamic and quantum chemistry methods, we have simulated the formation of ultrafine aerosol particles from sulfuric acid and hydrogen sulfuric monomer, with ammonia and dimethylamine, and calculated the thermodynamic parameters, such as the Gibbs free energy(Gf), enthalpy (H), entropy (S) and the reaction Gibbs free energy (Gr) of the dimers and individual trimers on the basis of rigid-rotor harmonic-oscillator (RRHO) approximation. The main results are as follows:As to the simulation and calculation methology, the structural optimization and spectrum calculation of H2SO4·HSO4- dimer have been used as criteria for the compariation about the results of three different level of ab initio simulations of pure DFT, Hybrid-DFT and the ADMM-hybrid-DFT. Our results show that Hybrid-DFT gives the most reliable results and would be chosen as the main methods for the subsequent calculations.The comparison of the thermodynamic properties of the H2SO4·HSO4- dimer in different atmospheric conditions, show that it is easier for sulfuric acid aerosol particles to be formed at higher altitude in the troposphere, where the actual partial pressure of sulfuric acid molecules and ions is relatively high. Ammonia and amine can promote the growth of neutral sulfuric acid clusters significantly, but have little effects on the ionic sulfuric acid clusters. Amine has more evident effects on the nucleation of both neutral and ionic clusters than that of ammonia. One possible mechanism for the difference might has relevance with the more proton transferr possibility for the amine.These results provide a theoretical basis for our further study on the association between GCR and Earth’s cloud coverage.