集体声子混合与同位素替代下的本征向量传输
Collective Phonon Mixing and Eigenvector Transport Under Isotope Substitution
AI总结：
研究通过同位素替代影响声子本征向量的连续传输，揭示复杂框架材料中振动特性在同位素替代下的连续轨迹。
摘要：
同位素替代修改核质量而不改变电子势能面，通常被解释为振动频率的简单缩放。然而在具有密集声子能级的固体中，质量替代作为质量加权动力学矩阵的参数Hermitian变形，生成连续的本征问题家族，其本征向量可在耦合子空间中发生显著旋转。本文通过非弹性中子散射和密度泛函理论晶格动力学计算研究了质子化和氘化ZIF-8。尽管许多振动模式表现出接近理想的质量缩放并保持其特征，但嵌入谱密集区域的模式显示显著的振动特征再分布，无法仅通过频率变化推断。由于非弹性中子散射强度直接与氢位移振幅加权，谱稀疏性和密集性提供了预测频率重整化或氘化下本征向量重新组织的实验指标。为建立物理有意义的模式对应关系，我们开发了具有重叠跟踪和显式稳定性诊断的绝热本征向量连续框架。这些结果表明，复杂框架材料中的振动特性最好理解为本征向量空间中的连续轨迹，并为分析密集声子系统中同位素诱导的谱流提供了一般框架。
英文摘要：
Isotopic substitution modifies nuclear masses without altering the electronic potential energy surface to first order and is therefore often interpreted as a simple rescaling of vibrational frequencies. In solids with dense phonon manifolds, however, mass substitution acts as a parametric Hermitian deformation of the mass-weighted dynamical matrix, generating a continuous family of eigenproblems whose eigenvectors can undergo substantial rotation within coupled subspaces. Here we investigate protiated and deuterated ZIF-8 using inelastic neutron scattering and density functional theory lattice-dynamics calculations. While many vibrational modes exhibit near-ideal mass scaling and preserve their character across isotopic endpoints, modes embedded in spectrally congested regions display pronounced redistribution of vibrational character that cannot be inferred from frequency shifts alone. Because inelastic neutron scattering intensity is directly weighted by hydrogen displacement amplitude, spectral sparsity and congestion provide experimental indicators of predictable frequency renormalisation or susceptibility to qualitative eigenvector reorganisation under deuteration. To establish physically meaningful mode correspondence, we develop an adiabatic eigenvector-continuation framework with overlap-based tracking and explicit stability diagnostics. These results show that vibrational identity in complex framework materials is best understood as a continuous trajectory in eigenvector space and provide a general framework for analysing isotope-induced spectral flow in dense phonon systems.
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