Formulation and density functional workflow for calculating the lifetime of vibrational modes of molecular adsorbates on solid surfaces due to vibration–phonon coupling are presented. The anharmonic coupling is invoked to give the correct description of the origin of temperature dependence. Using pyrrolidine (C₄H₉N) absorbed on the Cu(001) surface as a concrete example, we show that the anharmonic coupling can be one to two orders more significant than the harmonic interaction for the broadening of vibrational spectra, especially as temperature increases. These results challenge the common assumption that the anharmonic interaction is weak and call for attention of considering its effect in quantum relaxation and related problems.

中文翻译：

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吸附物振动模式弛豫的密度泛函研究：非谐相互作用的优势

介绍了用于计算固体表面由于振动-声子耦合作用而产生的分子吸附物的振动模式寿命的公式和密度函数工作流程。调用非谐波耦合以正确描述温度依赖性的起源。以在Cu（001）表面吸收的吡咯烷（C ₄ H ₉ N）为例，我们证明，对于振动谱的扩大，非谐耦合的谐波相互作用比谐波相互作用要大一到两个数量级，特别是随着温度的升高增加。这些结果挑战了非谐相互作用弱的普遍假设，并呼吁注意考虑其在量子弛豫和相关问题中的作用。