Finite electric displacement simulations of polar ionic solid-electrolyte interfaces: Application to NaCl(111)/aqueous NaCl solution.
Finite electric displacement simulations of polar ionic solid-electrolyte interfaces: Application to NaCl(111)/aqueous NaCl solution.
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DOI：
10.1063/1.5054843
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发表时间：
2018-09
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通讯作者：
T. Sayer;M. Sprik;Chao Zhang
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作者：
T. Sayer;M. Sprik;Chao Zhang
Tasker III型离子晶体的极性终端携带净表面电荷以及偶极矩，并且基本上不稳定。在与电解质接触时，这种极性表面可以通过从溶液中吸附抗衡离子以形成双电层来稳定。在以前的工作[T。Sayer等人，J. Chem. Phys 147，104702（2017）]，我们报道了基于经典力场的原型模型系统的分子动力学研究，即两侧与NaCl水溶液界面的NaCl（111）板。模拟中的一个严重障碍是平板的有限宽度允许固体中的电场干扰半无限系统界面处的理论电荷平衡[NaCl（111）的表面电荷密度的一半]。结果表明，施加一个有限的宏观场E来抵消内部电场，可以恢复界面处正确的电荷补偿。在本工作中，我们通过应用共轭电位移场D来扩展这种方法。使用D代替E作为控制变量的好处有两个方面：它不仅加快了模拟中极化的收敛，而且还导致了仅涉及预先已知的结构参数的偏置位移场的简洁表达式。这使得它是可行的研究电荷补偿现象的原型系统与密度泛函理论为基础的分子动力学，如在这项工作中所示。
Tasker type III polar terminations of ionic crystals carry a net surface charge as well as a dipole moment and are fundamentally unstable. In contact with electrolytes, such polar surfaces can be stabilized by adsorption of counterions from the solution to form electric double layers. In a previous work [T. Sayer et al., J. Chem. Phys 147, 104702 (2017)], we reported on a classical force field based molecular dynamics study of a prototype model system, namely, a NaCl(111) slab interfaced with an aqueous NaCl solution on both sides. A serious hurdle in the simulation is that the finite width of the slab admits an electric field in the solid perturbing the theoretical charge balance at the interface of semi-infinite systems [half the surface charge density for NaCl(111)]. It was demonstrated that the application of a finite macroscopic field E canceling the internal electric field can recover the correct charge compensation at the interface. In the present work, we expand this method by applying a conjugate electric displacement field D. The benefits of using D instead of E as the control variable are two fold: it does not only speed up the convergence of the polarization in the simulation but also leads to a succinct expression for the biasing displacement field involving only structural parameters which are known in advance. This makes it feasible to study the charge compensating phenomenon of this prototype system with density functional theory based molecular dynamics, as shown in this work.