Abstract An investigation of the frequency dependent dielectric polarizability of water molecules bound to clay mineral surfaces using molecular dynamic simulation is essential to improve understanding of the bulk electrical transport properties of shales in petrophysics and other clay science. The aim of the present study was to quantify the frequency-dependence of the complex permittivity of K+-smectite partially and fully saturated with water and to determine the relaxation frequency of the K+-smectite for pore size of ~1 nm and smectite matrix basal space of 1.66 nm with water saturations that varied from 20 to 100 wt% using molecular dynamics simulations. The simulation results of the dielectric spectra showed an unchanged polarization mechanism occurring within the K+-smectite with nano pore size, characterized by a water saturation dependent static permittivity. The characteristic frequency of the dielectric relaxation was found to be ~30 GHz for the system studied. The permittivity relaxation was found to be non-Debye type relaxation, with a circular arc locus providing a good representation of the simulated data. The deviation from pure Debye behavior reduced and the dielectric permittivity became much more significant as water saturation increases. The results presented here identified the dielectric relaxation as resulting from the orientational correlation of the water molecules near the K+-smectite surface and gave support to the idea that the relaxation frequency reflects the dimension of pores. This work constituted a novel contribution to the dielectric spectra of overall wet K+-smectite by extending the dielectric behavior of the clay mineral-water system to a microscopic level description.

中文翻译：

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粘土矿物介电特性的频率和水饱和度依赖性

摘要 使用分子动力学模拟研究与粘土矿物表面结合的水分子的频率相关介电极化率对于提高对岩石物理学和其他粘土科学中页岩的整体电传输特性的理解至关重要。本研究的目的是量化 K+-蒙脱石部分和完全被水饱和的复介电常数的频率依赖性，并确定 K+-蒙脱石在~1 nm 孔径和蒙脱石基体基础空间的弛豫频率1.66 nm 的水饱和度使用分子动力学模拟从 20 到 100 wt% 不等。介电光谱的模拟结果表明，在具有纳米孔径的 K+-蒙脱石中发生的极化机制没有改变，以水饱和度相关的静态介电常数为特征。对于所研究的系统，发现介电弛豫的特征频率为~30 GHz。发现介电常数弛豫是非德拜型弛豫，圆弧轨迹提供了模拟数据的良好表示。随着水饱和度的增加，与纯德拜行为的偏差减少，介电常数变得更加显着。这里介绍的结果确定了介电弛豫是由 K+-蒙脱石表面附近水分子的取向相关性引起的，并支持弛豫频率反映孔尺寸的想法。