Cu(111)表面负载Zn₃团簇的温度诱导重组：从最低能量结构到有限温度系综
Temperature-Induced Reorganization of Supported Zn$_3$ Clusters on Cu(111): From Minimum-Energy Structures to Finite-Temperature Ensembles
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中文总结 AI 辅助
该研究结合多种计算方法，发现Cu(111)表面负载Zn基团簇的热力学结构随温度变化，与0 K静态预测不同，凸显有限温度采样对催化剂建模的重要性。
中文摘要 AI 辅助
理解反应条件下催化活性位点的本质仍是多相催化领域的核心挑战。在工业甲醇合成用铜/氧化锌/氧化铝催化剂中，Cu界面处的小型Zn基物种长期被认为是活性位点候选者，但其原子尺度结构与稳定性仍存在争议。计算研究通常从优化后的0 K结构中识别此类物种，假设最低能量构型在反应条件下仍具代表性。本文结合机器学习原子间势加速的全局优化、分子动力学及增强采样自由能计算，研究Cu(111)基表面上0至450 K范围内负载的Zn₃(OH)₃与Zn₃(OH)₂CHOO团簇。尽管0 K时紧凑三角构型通常在最低能量结构中占优，但有限温度自由能计算显示，随温度升高会明显向延伸线性构型转变。该转变主要由熵稳定驱动，无法仅从势能推断。分子动力学进一步表明，团簇在纯净Cu(111)上具有显著迁移性，说明其长期存在不仅取决于构型稳定性，还依赖于表面迁移性。表面Zn合金化会强烈抑制扩散，从而稳定孤立的界面Zn物种。综上，负载Zn基团簇的热力学相关结构因焓与熵效应的竞争，可能与静态0 K预测存在根本差异。本研究结果凸显了仅从0 K结构识别催化活性位点的局限性，并强调了催化剂建模中显式有限温度采样的重要性。
英文摘要
Understanding the nature of catalytic active sites under reaction conditions remains a central challenge in heterogeneous catalysis. In industrial copper/zinc oxide/alumina catalysts for methanol synthesis, small Zn-based species at the Cu interface have long been proposed as active-site candidates, yet their atomic-scale structure and stability remain controversial. Computational studies typically identify such species from optimized 0 K structures, assuming that minimum-energy configurations remain representative under reaction conditions. Here, we combine machine-learning-interatomic-potential-accelerated global optimization, molecular dynamics, and enhanced-sampling free-energy calculations to investigate supported Zn$_3$(OH)$_3$ and Zn$_3$(OH)$_2$CHOO clusters on Cu(111)-based surfaces from 0 to 450 K. While compact triangular configurations are generally favored among minimum-energy structures at 0 K, finite-temperature free-energy calculations reveal a pronounced shift toward extended linear configurations with increasing temperature. This transition is driven primarily by entropic stabilization and cannot be inferred from potential energies alone. Molecular dynamics further shows substantial cluster mobility on pristine Cu(111), indicating that long-term persistence depends not only on configurational stability but also on surface mobility. Surface Zn alloying strongly suppresses diffusion, thereby stabilizing isolated interfacial Zn species. Together, these results show that thermodynamically relevant structures of supported Zn-based clusters can differ fundamentally from static 0 K predictions because of competing enthalpic and entropic effects. Our findings highlight the limitations of identifying catalytic active sites solely from 0 K structures and underscore the importance of explicit finite-temperature sampling in catalyst modeling.
