Low energy density is the principle obstacle for widespread adoption of dielectric capacitors for large-scale energy storage, and in polymer–ceramic nanocomposite systems the root cause is dielectric breakdown at the nanoscale interface. Interfacial effects in composites cannot be observed directly, due to the long-range effects of the surrounding media and the internal nature of the defects, so we need to relate quantities we can calculate to macroscale properties. We demonstrate in silico a novel approach to evaluate surface coatings for dielectric polymer nanocomposites to determine their effect on electrical breakdown a priori. We look at the electric field at the interface of barium titanate nanoparticles, in a general way, using first principles of density functional theory. The calculated induced electric field of several surface functionalized polymer–ceramic nanocomposites, chosen based on their wide range of different chemical features, shows that 7-octenyltrimethoxysilane will have the most increased ultimate breakdown voltage. We also compare two previously used metrics for quantifying breakdown in composite materials, polarizability and band gap and discuss their limitations. Experimental results should be used to further refine our model because functionalization position is critical to the induced electric field, but this position is difficult to definitively determine computationally because of steric and other effects present in real systems. Combined with experimental inputs, our new approach could be used to dramatically reduce the cost and the number of experiments needed to find new composite materials.

中文翻译：

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用于改进电容储能的纳米粒子-聚合物表面功能化的第一性原理建模

低能量密度是广泛采用介电电容器进行大规模储能的主要障碍，在聚合物-陶瓷纳米复合材料系统中，根本原因是纳米级界面的介电击穿。由于周围介质的长程效应和缺陷的内部性质，复合材料中的界面效应无法直接观察到，因此我们需要将可以计算的数量与宏观特性相关联。我们在计算机上展示了一种评估介电聚合物纳米复合材料的表面涂层的新方法，以确定它们对电击穿的先验影响。我们使用密度泛函理论的第一原理，以一般方式观察钛酸钡纳米粒子界面处的电场。根据其广泛的不同化学特征选择的几种表面功能化聚合物-陶瓷纳米复合材料的计算感应电场表明，7-辛烯基三甲氧基硅烷将具有最大的极限击穿电压。我们还比较了两个以前用于量化复合材料击穿的指标、极化率和带隙，并讨论了它们的局限性。实验结果应用于进一步完善我们的模型，因为功能化位置对感应电场至关重要，但由于实际系统中存在空间位阻和其他效应，因此很难通过计算明确确定该位置。结合实验输入，我们的新方法可用于显着降低成本和寻找新复合材料所需的实验数量。