Continuum solvent models have become a standard technique in the context of electronic structure calculations, yet no implementations have been reported capable to perform molecular dynamics at solid-liquid interfaces. We propose here such a continuum approach in a density functional theory framework using plane-wave basis sets and periodic boundary conditions. Our work stems from a recent model designed for Car–Parrinello simulations of quantum solutes in a dielectric medium D. A. Scherlis et al., J. Chem. Phys. 124, 074103 2006, for which the permittivity of the solvent is defined as a function of the electronic density of the solute. This strategy turns out to be inadequate for systems extended in two dimensions: the dependence of the dielectric function on the electronic density introduces a new term in the Kohn–Sham potential, which becomes unphysically large at the interfacial region, seriously affecting the convergence of the self-consistent calculations. If the dielectric medium is properly redefined as a function of the atomic coordinates, a good convergence is obtained and the constant of motion is conserved during the molecular dynamics simulations. The Poisson problem is solved using a multigrid method, and in this way Car–Parrinello molecular dynamics simulations of solid-liquid interfaces can be performed at a very moderate computational cost. This scheme is employed to investigate the acid-base equilibrium at the TiO2-water interface. The aqueous behavior of titania surfaces has stimulated a large amount of experimental research, but many open questions remain concerning the molecular mechanisms determining the chemistry of the interface. Here we make an attempt to answer some of them, putting to the test our continuum model.
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机译：在电子结构计算的背景下，连续溶剂模型已成为一种标准技术，但是还没有报道能够在固液界面上进行分子动力学的实现方法。在这里，我们在使用平面波基集和周期边界条件的密度泛函理论框架中提出了这种连续性方法。我们的工作源于一个最新模型，该模型专为Car-Parrinello模拟介电介质中的量子溶质D. A. Scherlis等，J。Chem。物理124，074103 2006，其中溶剂的介电常数定义为溶质电子密度的函数。事实证明，这种策略不足以扩展到二维系统：介电函数对电子密度的依赖性在Kohn-Sham势中引入了一个新术语，该势在界面区域变得物理上过大，严重影响了电势的收敛。自洽计算。如果适当地重新定义介电介质作为原子坐标的函数，则可以在分子动力学模拟过程中获得良好的收敛性并保持运动常数。泊松问题是使用多网格方法解决的，通过这种方法，可以以非常适中的计算成本执行固液界面的Car–Parrinello分子动力学模拟。该方案用于研究TiO 2-水界面处的酸碱平衡。二氧化钛表面的水行为刺激了大量的实验研究，但是关于决定界面化学性质的分子机制仍然存在许多悬而未决的问题。在这里，我们尝试回答其中的一些问题，以测试我们的连续体模型。
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