标题： 电子关联在活性空间之外在实现自旋-声子弛豫的定量预测中的作用 显示英文标题

标题： The Role of Electron Correlation Beyond the Active Space in Achieving Quantitative Predictions of Spin-Phonon Relaxation

摘要： 单分子磁体（SMMs）由于其强磁各向异性和长自旋弛豫时间，是分子尺度数据存储和处理的有前途的候选材料。 然而，随着温度升高，电子态与晶格振动之间的相互作用会加速自旋弛豫，显著限制了它们的实际应用。 最近，从头算模拟使得我们能够深入理解声子引起的磁性弛豫，但经常观察到与实验结果存在显著偏差。 分子的电子结构描述主要基于完全活性空间自洽场（CASSCF）计算，而活性空间之外的电子相关效应仍大多未被探索。 在本研究中，我们提供了使用后CASSCF多组态方法对SMMs中的自旋-声子弛豫进行的首次系统性研究，具体包括CASSCF之后的二阶微扰理论和多组态对密度泛函理论。 以基于Co(II)和Dy(III)的SMMs为例，我们分析了电子相关性如何在不同温度下影响自旋-声子弛豫速率，并将理论预测与实验观察进行了比较。 我们的研究结果表明，后CASSCF处理方法使得对基于Co(II)的SMMs实现定量预测成为可能。 然而，对于基于Dy(III)的体系，准确预测需要考虑额外的影响因素，这突显了进一步推进这些复杂体系中电子相关效应研究的紧迫性。 显示英文摘要

摘要： Single-molecule magnets (SMMs) are promising candidates for molecular-scale data storage and processing due to their strong magnetic anisotropy and long spin relaxation times. However, as temperature rises, interactions between electronic states and lattice vibrations accelerate spin relaxation, significantly limiting their practical applications. Recently, ab initio simulations have made it possible to advance our understanding of phonon-induced magnetic relaxation, but significant deviations from experiments have often been observed. The description of molecules' electronic structure has been mostly based on complete active space self-consistent field (CASSCF) calculations, and the impact of electron correlation beyond the active space remains largely unexplored. In this study, we provide the first systematic investigation of spin-phonon relaxation in SMMs with post-CASSCF multiconfigurational methods, specifically CAS followed by second-order perturbation theory and multiconfiguration pair-density functional theory. Taking Co(II)- and Dy(III)-based SMMs as case studies, we analyze how electron correlation influences spin-phonon relaxation rates across a range of temperatures, comparing theoretical predictions with experimental observations. Our findings demonstrate that post-CASSCF treatments make it possible to achieve quantitative predictions for Co(II)-based SMMs. For Dy(III)-based systems, however, accurate predictions require consideration of additional effects, underscoring the urgent necessity of further advancing the study of the effects of electronic correlation in these complex systems.