Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
J Phys Chem A. 2010 Apr 29;114(16):5414-28. doi: 10.1021/jp101092v.
The effect of hydrogen-bond cooperativity on self- and cross-aggregation of multiple polar species in supercritical carbon dioxide was investigated using both ab initio calculations and Monte Carlo simulations. Ab initio calculations indicate that hydrogen-bond cooperativity has a significant impact on the cluster size, but does not greatly influence the composition of clusters. The microscopic structures in the ethanol + CO(2) and acetic acid + CO(2) binary mixtures were first studied using Monte Carlo simulations with a strict set of criteria for hydrogen bonding, and a satisfactory agreement with experimental data was achieved. The state of microscopic phase separation in the ethanol + water + CO(2) and acetic acid + water + CO(2) ternary mixtures was then extensively investigated, indicating that the size and composition of aggregates are strongly dependent on the mixing ratio. Moreover, hydrogen-bond cooperativity must be considered to acquire more thorough understanding of the hydration process. On the basis of the detailed distributions of aggregate size and structure, a new two-staged hydration mechanism was finally proposed for the ternary solutions.
采用从头算和蒙特卡罗模拟相结合的方法研究了氢键协同效应对超临界二氧化碳中多种极性物质自聚和共聚的影响。从头算计算表明氢键协同效应对团簇大小有显著影响，但对团簇组成影响不大。利用严格氢键标准的蒙特卡罗模拟首次研究了乙醇+CO2 和乙酸+CO2 二元混合物的微观结构，与实验数据吻合良好。然后，详细研究了乙醇+水+CO2 和乙酸+水+CO2 三元混合物的微观相分离状态，表明聚集体的大小和组成强烈依赖于混合比。此外，必须考虑氢键协同效应对水化过程的更全面理解。基于聚集体大小和结构的详细分布，最后提出了一个新的用于三元溶液的两阶段水化机制。
