arXiv 2602.077052026-02physics.chem-ph

Pauli排斥力、静电学和场非均匀性对蓝移和红移振动探针分子的相互作用

The Interplay of Pauli Repulsion, Electrostatics, and Field Inhomogeneity for Blueshifting and Redshifting Vibrational Probe Molecules

Kenneth S. Pitzer Theory Center and Department of Chemistry（肯尼斯·S·皮策理论中心及化学系）；Chemical Sciences Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室化学科学部）；Departments of Bioengineering and Chemical and Biomolecular Engineering University of California, Berkeley, CA, 94720 USA（加州大学伯克利分校生物工程系及化学与分子生物工程系）

R. Allen LaCour, Ruoqi Zhao, Teresa Head-Gordon

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AI总结：

研究揭示了振动探针分子在不同分子间相互作用和场非均匀性影响下的红移与蓝移机制，通过计算分析发现静电作用需克服Pauli排斥主导的蓝移贡献才能产生红移，场非均匀性进一步影响探针频率变化。

摘要：

许多分子的振动频率对分子间电场敏感，使其能够探测复杂分子环境中的电场。然而，通常不清楚探针是响应局部电场还是其他分子间相互作用，抑制了频率和有效性作为探针的解释。特别是那些在氢键配置中蓝移而非典型红移的分子。本文通过计算研究了红移与蓝移的原因，发现当静电相互作用足够强以克服Pauli排斥主导的蓝移贡献时，才会出现红移。此外，场非均匀性可显著改变许多探针的频率，使其增强或抵消均匀场预期的位移。红移被电场非均匀性增强，否则场非均匀性会削弱静电贡献相对于Pauli排斥，导致蓝移。进一步计算表明，探针对场非均匀性的响应可通过考虑参与伸缩模式的原子质量及电场符号来理解。我们的结果应有助于谱探针的使用和解释，以及将其与更复杂系统中的电场联系起来。

英文摘要：

Many molecules' vibrational frequencies are sensitive to intermolecular electric fields, enabling them to probe the field in complex molecular environments. However, it is often unclear whether the probe is responding to the local electric field or other types of intermolecular interactions, inhibiting interpretation of the frequency and effectiveness as probes. This is especially true of molecules whose vibrational frequencies blueshift instead of the more typical redshift in hydrogen bonding configurations. Here we computationally investigate the causes of redshifting versus blueshifting over a range of vibrational reporters. First, we apply adiabatic energy decomposition analysis to a paradigmatic set of probes, finding that redshifting only occurs when electrostatic interactions are strong enough to overcome the dominant and large blueshifting contribution of Pauli repulsion. Furthermore, we demonstrate that field inhomogeneity can further shift the frequency of many probes substantially to either reinforce or counteract the shift expected from a homogeneous field. We find that redshifting is reinforced by electric field inhomogeneity, otherwise field inhomogeneity further weakens the electrostatic contribution relative to Pauli repulsion, leading to blueshifting. Further calculations indicate that the probe's response to field inhomogeneity can be understood by considering the mass of the atoms involved in the stretching mode and sign of the electric field. In explaining the interplay of different intermolecular interactions and field inhomogeneity for many probes, our results should enable the use and interpretation of spectroscopic probes and their connection to electric fields in more complex systems.

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