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Structural and Dynamical Properties of Alkaline Earth Metal Halides in Supercritical Water: Effect of Ion Size and Concentration
The Journal of Physical Chemistry B ( IF 3.3 ) Pub Date : 2017-11-10 00:00:00 , DOI: 10.1021/acs.jpcb.7b07690
Sonanki Keshri 1 , B. L. Tembe 1
Affiliation  

Constant temperature–constant pressure molecular dynamics simulations have been performed for aqueous alkaline earth metal chloride [M2+–Cl (M = Mg, Ca, Sr, and Ba)] solutions over a wide range of concentrations (0.27–5.55 m) in supercritical (SC) and ambient conditions to investigate their structural and dynamical properties. A strong influence of the salt concentration is observed on the ion–ion pair correlation functions in both ambient and SC conditions. In SC conditions, significant clustering is observed in the 0.27 m solution, whereas the reverse situation is observed at room temperature and this is also supported by the residence times of the clusters. The concentration and ion size (cation size) seem to have opposite effects on the average number of hydrogen bonds. The simulation results show that the self-diffusion coefficients of water, cations, and the chloride ion increase with increasing temperature, whereas they decrease with increasing salt concentration. The cluster size distribution shows a strong density dependence in both ambient and SC conditions. In SC conditions, cluster sizes display a near-Gaussian distribution, whereas the distribution decays monotonically in ambient conditions.

中文翻译:

碱土金属卤化物在超临界水中的结构和动力学性质:离子尺寸和浓度的影响

对碱土金属氯化物[M 2+ –Cl (M = Mg,Ca,Sr和Ba)[M 2+ –Cl (M = Mg,Ca,Sr和Ba)]溶液进行了恒温恒压分子动力学模拟,其浓度范围很广(0.27–5.55 m)在超临界(SC)和环境条件下研究其结构和动力学特性。在环境和SC条件下,都观察到盐浓度对离子-离子对相关函数的强烈影响。在南太平洋条件下,在0.27 m处观察到明显的聚类解决方案,而在室温下观察到相反的情况,这也由簇的停留时间支持。浓度和离子尺寸(阳离子尺寸)似乎对平均氢键数具有相反的影响。模拟结果表明,水,阳离子和氯离子的自扩散系数随温度的升高而增加,而随盐浓度的升高而减小。簇的大小分布在环境和SC条件下都表现出强烈的密度依赖性。在SC条件下,簇大小显示接近高斯分布,而在环境条件下该分布单调衰减。
更新日期:2017-11-11
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