Tresset Guillaume
Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos 04-01, Singapore 138669.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Dec;78(6 Pt 1):061506. doi: 10.1103/PhysRevE.78.061506. Epub 2008 Dec 30.
We establish a generalized Poisson-Fermi formalism to compute the electrostatic potential next to charged surfaces in the presence of multiple ion species with different sizes. A generalized Fermi-like ion distribution is deduced from the excess free energy, after expansion of the functional entropy of free space in which the ions have all the same size. The ion distribution is expressed in terms of the bulk volume fractions of each ion species rather than their bulk concentrations so as to account for the excluded volumes. We present size correlations effects such as underscreening and ion stratification, which have not been investigated before with such a simple theory. The change of dielectric properties across the space, arising from the finite spatial occupancy of ions, can be solved self-consistently through the Bruggeman model. The generalized Poisson-Fermi formalism is anticipated to be useful for interpreting electrophoretic mobility measurements and for computing the electrostatic potential over the surface of biomolecules in ionic solutions.
我们建立了一种广义泊松 - 费米形式体系，用于计算在存在多种不同大小离子物种的情况下，带电表面附近的静电势。在将离子大小均相同的自由空间的泛函熵展开后，从过剩自由能推导出一种广义的类费米离子分布。离子分布用每种离子物种的体相体积分数而非体相浓度来表示，以便考虑排除体积。我们展示了诸如欠屏蔽和离子分层等大小关联效应，这些效应此前尚未用如此简单的理论进行研究。由离子有限的空间占有率引起的整个空间介电性质的变化，可以通过布鲁格曼模型自洽求解。预计广义泊松 - 费米形式体系对于解释电泳迁移率测量以及计算离子溶液中生物分子表面的静电势将是有用的。
