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arXiv 2308.09271cond-mat.mtrl-sciphysics.chem-phphysics.comp-ph
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环境及极端压力-温度条件下石墨烯纳米限域水的 Raman 和 IR 光谱:一项第一性原理研究

Raman and IR spectra of water under graphene nanoconfinement at ambient and extreme pressure-temperature conditions: a first-principles study

Rui Hou, Chu Li, Ding Pan

AI总结:

该研究用第一性原理模拟计算石墨烯纳米限域水在环境及极端温压下的 Raman/IR 光谱,揭示氢键网络、离子相和超离子流体转变特征。

摘要:

水的纳米限域可导致其物理和化学性质与体相水相比出现显著差异。然而,人们对这些性质仍缺乏详细的分子层面理解。Raman 和红外等振动光谱是研究水的结构与动力学的常用实验工具,并常辅以原子模拟来解释实验光谱;但在环境条件下,使用第一性原理方法研究纳米限域水的理论光谱工作很少,更不用说在极端压力-温度条件下。本文中,我们利用 ab initio 模拟计算了环境及极端压力-温度条件下被石墨烯纳米限域的水的 Raman 和 IR 光谱。结果揭示了石墨烯限域引起的 Raman 伸缩带和低频带变化。我们还发现光谱证据表明,纳米限域显著改变了体相水中通常存在的四面体氢键网络。此外,我们在约 10 GPa、1000 K 的 Raman 光谱中观察到一个异常弯曲带,其归因于限域离子水独特的分子结构。我们还发现,在约 20 GPa、1000 K 时,限域水转变为超离子流体,使 IR 伸缩带难以识别。最后,我们计算了限域水在离子相和超离子相中的离子电导率。结果突显了 Raman 和 IR 光谱在宽压力-温度范围内研究纳米限域水结构与动力学的有效性。我们预测的 Raman 和 IR 光谱可为未来实验提供有价值的指导。

英文摘要:

The nanoconfinement of water can result in dramatic differences in its physical and chemical properties compared to bulk water. However, a detailed molecular-level understanding of these properties is still lacking. Vibrational spectroscopy, such as Raman and infrared, is a popular experimental tool for studying the structure and dynamics of water, and is often complemented by atomistic simulations to interpret experimental spectra, but there have been few theoretical spectroscopy studies of nanoconfined water using first-principles methods at ambient conditions, let alone under extreme pressure-temperature conditions. Here, we computed the Raman and IR spectra of water nanoconfined by graphene at ambient and extreme pressure-temperature conditions using ab intio simulations. Our results revealed alterations in the Raman stretching and low-frequency bands due to the graphene confinement. We also found spectroscopic evidence indicating that nanoconfinement considerably changes the tetrahedral hydrogen bond network, which is typically found in bulk water. Furthermore, we observed an unusual bending band in the Raman spectrum at ~10 GPa and 1000 K, which is attributed to the unique molecular structure of confined ionic water. Additionally, we found that at ~20 GPa and 1000 K, confined water transformed into a superionic fluid, making it challenging to identify the IR stretching band. Finally, we computed the ionic conductivity of confined water in the ionic and superionic phases. Our results highlight the efficacy of Raman and IR spectroscopy in studying the structure and dynamics of nanoconfined water in a large pressure-temperature range. Our predicted Raman and IR spectra can serve as a valuable guide for future experiments.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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