Density functional theory of gas-liquid phase separation in dilute binary mixtures
Density functional theory of gas-liquid phase separation in dilute binary mixtures
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DOI：
10.1088/0953-8984/28/24/244012
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发表时间：
2016-06-22
影响因子：
2.7
通讯作者：
Onuki, Akira
中科院分区：
文献类型：
--
作者：
Okamoto, Ryuichi;Onuki, Akira
我们用密度泛函理论研究了稀二元混合物相分离态的静力学和动力学。在我们的体系中，液体和气体的溶剂化化学势之差δ mu(s)（吉布斯转移能）远大于每个溶质粒子的热能k(B)T，溶质粒子之间的吸引相互作用弱于溶剂粒子之间的吸引相互作用。在这些条件下，饱和蒸汽压增加了k(B)Tn(2)(l)exp(δ mu(s)/k(B)T)，其中n(2)(l)是加入液体中的溶质密度。对于exp(δ mu(s)/k(B)T) >> 1，在低溶质密度的液体中诱导相分离，新相保持气态，即使液体压强在溶剂的共存曲线之外。这就解释了为什么在周围的水中会有溶解气体形成稳定的纳米气泡。我们计算了平面和球面界面上的密度和应力分布，其中表面张力随着界面溶质吸附的增加而降低。我们实现了半径约为30 nm的稳定富溶质气泡，使自由能泛函最小化。然后，我们研究了在周围液体减压后，气泡周围的动力学，其中气泡经历了阻尼振荡。此外，我们还给出了表面张力和界面应力张量的精确近似表达式。
We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas Delta mu(s) (the Gibbs energy of transfer) is considerably larger than the thermal energy k(B)T for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by k(B)Tn(2)(l)exp(Delta mu(s)/k(B)T), where n(2)(l) is the solute density added in liquid. For exp(Delta mu(s)/k(B)T) >> 1, phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor.