We propose a new approach to obtain ultra-high piezoelectric coefficients that can be infinitely large theoretically, where ferroelectrics with strain-sensitive Curie temperature are necessary. We show the first-principles plus Monte Carlo simulation evidence that many hydrogen-bonded ferroelectrics (e.g. organic PhMDA) can be ideal candidates, which are also flexible and lead-free. Owing to the specific features of hydrogen bonding, their proton hopping barrier will drastically increase with prolonged proton transfer distance, while their hydrogen-bonded network can be easily compressed or stretched due to softness of hydrogen bonds. Their barriers as well as the Curie temperature can be approximately doubled upon a tensile strain as low as 2%. Their Curie temperature can be tuned exactly to room temperature by fixing a strain in one direction, and in another direction, an unprecedented ultra-high piezoelectric coefficient of 2058 pC/N can be obtained. This value is even underestimated and can be greatly enhanced when applying a smaller strain. Aside from sensors, they can also be utilized for converting either mechanical or thermal energies into electrical energies due to high pyroelectric coefficients.

中文翻译：

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氢键系统中的超高压电系数和应变敏感居里温度

我们提出了一种获得理论上可以无限大的超高压电系数的新方法，其中需要具有应变敏感居里温度的铁电体。我们展示了第一性原理加上蒙特卡罗模拟证据，表明许多氢键铁电体（例如有机 PhMDA）可以是理想的候选材料，它们也是灵活且无铅的。由于氢键的特殊特性，它们的质子跳跃势垒会随着质子转移距离的延长而急剧增加，而由于氢键的柔软性，它们的氢键网络很容易被压缩或拉伸。当拉伸应变低至 2% 时，它们的势垒和居里温度可以大约翻倍。通过在一个方向上固定应变，它们的居里温度可以精确地调整到室温，另一个方向，可以获得前所未有的2058 pC/N的超高压电系数。这个值甚至被低估了，当施加较小的应变时可以大大提高。除了传感器之外，由于热释电系数高，它们还可用于将机械能或热能转换为电能。