Correlation between surface tension and void fraction in ionic liquids.
Correlation between surface tension and void fraction in ionic liquids.
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DOI：
10.1021/jp8027929
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
C. Larriba;Y. Yoshida;J. Fernández de la Mora
中科院分区：
文献类型：
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作者：
C. Larriba;Y. Yoshida;J. Fernández de la Mora
对离子液体（IL）的表面张力γ的已发表的和新的数据进行系统化的努力是基于无量纲表面张力参数γ V v（2/3）/ kT是空隙率x v = V v/Vm的函数的假设。空隙体积V v被定义为离子对占据的液体体积V m（从阳离子和阴离子质量和液体密度测量已知）与阳离子和阴离子体积的总和V（+）+ V（-）（从晶体结构已知）之间的差，而kT是热能。我们的假设γ Vm（2/3）/ kT = G（xv）最初是基于腔理论。然后基于周期性晶格建模对其进行细化，其揭示了每个晶胞的空隙数量N（因此无量纲表面张力）必须取决于x v。针对在宽温度范围内可获得表面张力和密度数据的五种离子液体的数据来测试我们的假设，几乎将所有这些数据折叠在单个曲线G（x v）上，条件是在V（+）和V（-）的已发表晶体学数据上引入轻微（4%）自洽修改。尝试将无机熔融盐的表面张力与温度数据关联起来也同样成功，但代价是公布的离子半径发生了较大的变化（K为8.8%; I为3.3%）。离子液体和无机盐的塌陷G（xv）曲线在xv空间上没有任何重叠，并且似乎彼此不同。伽玛和x v之间的关系的存在是合理的一个简单的毛细管模型最小化的能量。我们在将表面张力与空隙率相关联方面的成功也可以应用于其他液体性质。
An effort to systematize published and new data on the surface tension gamma of ionic liquids (ILs) is based on the hypothesis that the dimensionless surface tension parameter gamma V v (2/3)/ kT is a function of the void fraction x v = V v/ V m. The void volume V v is defined as the difference between the liquid volume V m occupied by an ion pair (known from cationic and anionic masses and liquid density measurements) and the sum V (+) + V (-) of the cationic and anionic volumes (known from crystal structures), while kT is the thermal energy. Our hypothesis that gamma V m (2/3)/ kT = G( x v) is initially based on cavity theory. It is then refined based on periodic lattice modeling, which reveals that the number N of voids per unit cell (hence the dimensionless surface tension) must depend on x v. Testing our hypothesis against data for the five ILs for which surface tension and density data are available over a wide range of temperatures collapses all of these data almost on a single curve G( x v), provided that slight (4%) self-consistent modifications are introduced on published crystallographic data for V (+) and V (-). An attempt to correlate the surface tension vs temperature data available for inorganic molten salts is similarly successful, but at the expense of larger shifts on the published ionic radii (8.8% for K; 3.3% for I). The collapsed G( x v) curves for ILs and inorganic salts do not overlap anywhere on x v space, and appear to be different from each other. The existence of a relation between gamma and x v is rationalized with a simple capillary model minimizing the energy. Our success in correlating surface tension to void fraction may apply also to other liquid properties.