Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, von-Danckelmann-Platz 4, D-06120 Halle (Saale), Germany.
Molecules. 2021 Mar 26;26(7):1875. doi: 10.3390/molecules26071875.
We present a novel method for the computation of well-defined optimized atomic partial charges and radii from the total electron density. Our method is based on a two-step radical Voronoi tessellation of the (possibly periodic) system and subsequent integration of the total electron density within each Voronoi cell. First, the total electron density is partitioned into the contributions of each molecule, and subsequently the electron density within each molecule is assigned to the individual atoms using a second set of atomic radii for the radical Voronoi tessellation. The radii are optimized on-the-fly to minimize the fluctuation (variance) of molecular and atomic charges. Therefore, our method is completely free of empirical parameters. As a by-product, two sets of optimized atomic radii are produced in each run, which take into account many specific properties of the system investigated. The application of an on-the-fly interpolation scheme reduces discretization noise in the Voronoi integration. The approach is particularly well suited for the calculation of partial charges in periodic bulk phase systems. We apply the method to five exemplary liquid phase simulations and show how the optimized charges can help to understand the interactions in the systems. Well-known effects such as reduced ion charges below unity in ionic liquid systems are correctly predicted without any tuning, empiricism, or rescaling. We show that the basis set dependence of our method is very small. Only the total electron density is evaluated, and thus, the approach can be combined with any electronic structure method that provides volumetric total electron densities-it is not limited to Hartree-Fock or density functional theory (DFT). We have implemented the method into our open-source software tool TRAVIS.
我们提出了一种从总电子密度计算定义明确的优化原子部分电荷和半径的新方法。我们的方法基于系统的两步激进 Voronoi 胞腔划分，随后在每个 Voronoi 胞腔中积分总电子密度。首先，将总电子密度划分为每个分子的贡献，然后使用激进 Voronoi 胞腔的第二组原子半径将电子密度分配给各个原子。半径在运行时进行优化，以最小化分子和原子电荷的波动（方差）。因此，我们的方法完全没有经验参数。作为副产品，在每次运行中都会生成两组优化的原子半径，这些半径考虑了所研究系统的许多特定性质。在线插值方案的应用减少了 Voronoi 积分中的离散化噪声。该方法特别适用于周期性体相系统中部分电荷的计算。我们将该方法应用于五个示例液相模拟，并展示了优化后的电荷如何帮助理解系统中的相互作用。无需任何调整、经验或重新缩放，就可以正确预测离子液体系统中离子电荷低于单位的常见效应。我们表明，我们方法的基组依赖性非常小。仅评估总电子密度，因此，该方法可以与提供体积总电子密度的任何电子结构方法结合使用——它不仅限于 Hartree-Fock 或密度泛函理论（DFT）。我们已经将该方法实现到我们的开源软件工具 TRAVIS 中。
