A Density Functional Theory Study of the Hydrates of 2NH_3：H_2SO_4 and Its Implications for the Formation of Atmosphere Particles
A Density Functional Theory Study of the Hydrates of 2NH_3：H_2SO_4 and Its Implications for the Formation of Atmosphere Particles
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发表时间：
2010
影响因子：
2.2
通讯作者：
Zhao Ya-ying;Y. ZengEddy;Zhang Xi-hui;Ma Lin;Tao Fu-ming
中科院分区：
文献类型：
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作者：
Zhao Ya-ying;Y. ZengEddy;Zhang Xi-hui;Ma Lin;Tao Fu-ming
用密度泛函理论在B3LYP/6-311++G(d，p)水平上研究了n=0~4时2NH3：H2SO4：nH2O的水合物。当n=0和1时，最稳定的团簇中的中性分子自发形成，并被确定为单体物种的氢键分子络合物。在最稳定的2NH3：H2SO4：nH2O(n=2，3，4)团簇中自发形成双离子(含NH4+和HSO4-阴离子的簇合物)或甚至三元离子(含两个NH4+阳离子和一个SO42-阴离子的簇合物)。还计算了结合和增量缔合的能量学。由于形成中性(最稳定)和双离子(次稳定)异构体的自由能大致相等，所以在2NH3：H2SO4：2H2O之前，双离子在能量上是不有利的。在室温下，当ΔG≈-2kcal/m ol时，自由H2O与2NH3：H2SO4：NH2O的增量缔合自由能在n=2时最大。2NH3：H_2SO_4：N_2O、NH_3：H_2SO_4：N_2O和H_2SO_4：N_2O团簇的增量缔合能比较表明，NH_3在大气颗粒物成核过程中起着重要作用。
Density functional theory was used at the B3LYP/6-311++G(d,p) level of theory to study the hydrates of 2NH3:H2SO4:nH2O for n = 0～4. Neutrals of the most stable clusters, when n = 0 and 1, spontaneously formed and were determined to be hydrogen-bonded molecular complexes of monomeric species. Double ions (clusters containing a NH4+ cation and a HSO4- anion) or even ternary ions (clusters with two NH4+ cations and one SO42- anion) spontaneously formed in the most stable clusters of 2NH3:H2SO4:nH2O (n = 2, 3, 4). The energetics of binding and incremental association was also calculated. Double ions are not energetically favorable until 2NH3:H2SO4:2H2O because of the about equal free energies for forming the neutral (the most stable) and double ion (the second stable) isomers. The free energy of incremental association from free H2O and 2NH3:H2SO4:nH2O has a maximum at n = 2 at room temperature with ΔG ≈ –2 kcal/mol. The comparison of incremental association energies between 2NH3:H2SO4:nH2O, NH3:H2SO4:nH2O and H2SO4:nH2O clusters revealed that NH3 plays an important role in the atmospheric particle nucleation.