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arXiv 0904.4887physics.chem-phphysics.comp-ph
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连续介质固液界面的第一性原理分子动力学模拟

First-principles molecular dynamics simulations at solid-liquid interfaces with a continuum solvent

Veronica M. Sanchez, Mariela Sued, Damian A. Scherlis

摘要:

连续介质溶剂模型已经成为电子结构计算的标准技术,然而,还没有报道能够在固-液界面执行分子动力学的实现。我们建议在这里这样一个连续的DFT框架中的方法,使用平面波基组和周期性的边界条件。我们的工作源于最近的模型设计的量子溶质在电介质中的Car-Parrinello模拟[J. Chem. Phys. 124,74103(2006)],其中溶剂的介电常数被定义为溶质的电子密度的函数。这种策略被证明是不够的系统扩展在两个维度上,通过引入新的项的Kohn-Sham势变得非物理大的界面区域,严重影响收敛。在分子动力学模拟中,如果将介质适当地重新定义为原子坐标的函数,则可以获得良好的收敛性,并且运动常数保持不变。此外,一个显着的增益效率可以实现,如果模拟框被划分为两个,解决泊松问题分别为“干”区使用快速傅立叶变换,并为溶剂化或“湿”区使用多重网格方法。最后,这两种解决方案结合在一个自洽的程序,并在这种方式中的Car-Parrinello分子动力学模拟的固液界面,可以在一个非常温和的计算成本。该方案被用来研究在TiO 2-水界面的酸碱平衡。

英文摘要:

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 DFT framework, using plane-waves 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 [J. Chem. Phys. 124, 74103 (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, by introducing new term in the Kohn-Sham potential which becomes unphysically large at the interfacial region, seriously affecting the convergence. 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. Moreover, a significant gain in efficiency can be achieved if the simulation box is partitioned in two, solving the Poisson problem separately for the "dry" region using fast Fourier transforms, and for the solvated or "wet" region using a multigrid method. Eventually both solutions are combined in a self-consistent procedure, 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.

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