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Tailoring Superatomic Stability with Transition Metals in Silicon Cages: Shrinking to M@Si15 (M = Re, Os, Ir) 利用硅笼中的过渡金属定制超原子稳定性:收缩至 M@Si15(M = Re、Os、Ir)
IF 6.475 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 DOI: 10.1021/acs.jpclett.4c02797
Takumi Ichikawa, Kazuya Terasaka, Ayaka Sasaki, Atsushi Nakajima
The design of materials with intriguing electronic properties is crucial for advancing nanoscale technologies, where precise control over atomic structure and electronic behavior is essential. Metal-encapsulating silicon cage superatoms (SAs) provide a new paradigm for molecular-scale material design, allowing fine-tuning of both structure and electronic characteristics. The formation of superatoms mimicking halogens, noble gases, and alkali metals has been well-studied, particularly with M@Si16, where early transition metals from groups 3 to 5 stabilize within a Si16 cage, achieving a 68-electron configuration. For late transition metals with excess electrons, a Si15 cage offers enhanced stability by fulfilling the 68-electron rule with one fewer Si atom. This research synthesizes Si15 cage-SAs with rhenium (Re) from group 7 and iridium (Ir) from group 9 on p-type and n-type organic substrates. The stability of Re@Si15 and Ir@Si15 is evaluated via oxidative reactivity with X-ray photoelectron spectroscopy and theoretical calculations, including osmium (Os) from group 8. Re@Si15, Os@Si150, and Ir@Si15+ exhibit superatomic behaviors similar to halogens, noble gases, and alkali metals due to the 68-electron shell closure. Among them, Re@Si15 on p-type organic substrates shows superior electronic and geometric properties. These findings advance our understanding of M@Sin systems for transition metals, addressing longstanding questions about their properties at n = 15 and 16.
设计具有迷人电子特性的材料对于推动纳米技术的发展至关重要,因为在纳米技术中,对原子结构和电子行为的精确控制至关重要。金属封装硅笼超原子(SAs)为分子尺度材料设计提供了一种新的范例,允许对结构和电子特性进行微调。模拟卤素、惰性气体和碱金属的超原子的形成已得到深入研究,特别是 M@Si16,其中第 3 至第 5 族的早期过渡金属稳定在 Si16 笼中,实现了 68 电子构型。对于电子过剩的晚期过渡金属来说,Si15笼通过减少一个Si原子来满足68电子规则,从而增强了稳定性。这项研究在 p 型和 n 型有机基底上合成了含有 7 族铼(Re)和 9 族铱(Ir)的 Si15 笼状砷化镓。通过 X 射线光电子能谱和理论计算评估了 Re@Si15 和 Ir@Si15 的氧化反应稳定性,其中包括第 8 族的锇(Os)。其中,P 型有机基底上的 Re@Si15- 显示出卓越的电子和几何特性。这些发现增进了我们对过渡金属 M@Sin 系统的了解,解决了有关它们在 n = 15 和 16 时的性质的长期问题。
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引用次数: 0
Insights into Chemical Bonding Modes and Heat Transport at the Molecular Level. 洞察分子水平的化学键合模式和热传递。
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-10-31 DOI: 10.1021/acs.jpclett.4c02325
Shintaro Fujii, Yoshiaki Shoji, Yuma Masuda, Takanori Fukushima, Tomoaki Nishino

Despite the demand for nanoscale thermal management technologies of material surfaces and interfaces using organic molecules, heat transport properties at the single molecular level remain elusive due to the experimental difficulty of measuring temperature at the nanoscopic scale. Here we show how chemical bonding modes can affect the heat transport properties of single molecules. We focused on four molecular systems: benzylthiol linked to another phenyl group by either a triple (compound 1), double (3), or amide (4) bond and a common linear alkanethiol (2), all of which are nearly identical in molecular length. We prepared binary self-assembled monolayers (SAMs) using 1 as a common reference in combination with 2-4 and investigated their relative heat transport properties using scanning thermal microscopy (SThM). Two-dimensional temperature mapping of the binary SAMs showed that C≡C and C=C bonds provide more effective pathways for heat transport compared to C-C bonds. Since the amide molecule has resonance structures with C=N double bond character, we expected that its heat transport properties would be comparable to those of the thiols containing triple or double bonds. However, the heat transport properties of this molecule prevailed over the others, most likely due to the formation of additional heat transport pathways caused by intermolecular hydrogen bonding. These findings may provide important guidelines for the design of organic materials for nanoscale thermal management.

尽管需要利用有机分子对材料表面和界面进行纳米级热管理技术,但由于在纳米尺度上测量温度的实验难度很大,单分子水平的热传输特性仍然难以捉摸。在此,我们展示了化学键模式如何影响单分子的热传输特性。我们重点研究了四个分子体系:通过三键(化合物 1)、双键(3)或酰胺键(4)与另一个苯基相连的苄硫醇,以及常见的线性烷硫醇(2),它们的分子长度几乎完全相同。我们以 1 为共同参照物,结合 2-4 制备了二元自组装单层 (SAM),并使用扫描热显微镜 (SThM) 研究了它们的相对热传输特性。二元 SAM 的二维温度图显示,与 C-C 键相比,C≡C 键和 C=C 键提供了更有效的热传递途径。由于酰胺分子具有 C=N 双键共振结构,我们预计其热传输特性将与含有三键或双键的硫醇相当。然而,该分子的热传导特性优于其他分子,这很可能是由于分子间氢键形成了额外的热传导途径。这些发现可为设计用于纳米级热管理的有机材料提供重要指导。
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引用次数: 0
Synaptic Properties of an Interfacial Memristor Based on a Ga2O3/Nb:SrTiO3 Heterojunction. 基于 Ga2O3/Nb:SrTiO3 异质结的界面记忆器的突触特性
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-10-31 DOI: 10.1021/acs.jpclett.4c02548
Youhong Wang, Wei Hu, Kaijin Kang, Caili Dong, Xiaosheng Tang

Memristors have been extensively studied for tremendous potential for future neuromorphic computing hardware applications because of their ability to imitate biological synaptic processes. Herein, we report an interfacial memristor based on a Ga2O3/Nb:SrTiO3 heterojunction that shows stable bipolar resistive switching behavior, long retention time, and high switching ratio. The conductance of the Au/Ga2O3/Nb:SrTiO3/In memristor can be gradually modulated under the voltage sweep mode as well as positive and negative pulse voltage stimulations, respectively, thus realizing the long-term potentiation/depression characteristics of the simulated biological synapse. A neural network based on the prepared memristor was built to recognize the handwritten picture data set with a recognition accuracy of 92.78% by using the NeuroSimV3.0 platform. Our work indicates that the Ga2O3/Nb:SrTiO3 heterojunction memristor has significant potential in a neuromorphic computing system.

忆阻器具有模仿生物突触过程的能力,因此在未来神经形态计算硬件应用中具有巨大潜力,已被广泛研究。在此,我们报告了一种基于 Ga2O3/Nb:SrTiO3 异质结的界面忆阻器,它具有稳定的双极电阻开关行为、较长的保持时间和较高的开关比。Au/Ga2O3/Nb:SrTiO3/In Memristor 的电导率可分别在电压扫描模式和正负脉冲电压刺激下逐渐调制,从而实现模拟生物突触的长期增效/抑制特性。利用 NeuroSimV3.0 平台,构建了基于所制备的忆阻器的神经网络,用于识别手写图片数据集,识别准确率达到 92.78%。我们的工作表明,Ga2O3/Nb:SrTiO3异质结忆阻器在神经形态计算系统中具有巨大潜力。
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引用次数: 0
Slope of the Delocalization Function Is Proportional to Analytical Hardness. 脱焦函数的斜率与分析硬度成正比
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-11-04 DOI: 10.1021/acs.jpclett.4c02263
Bin Wang, Paul Geerlings, Farnaz Heidar-Zadeh, Paul W Ayers, Frank De Proft

Conceptual Density Functional Theory (CDFT) has been extended beyond its traditional role in elucidating chemical reactivity to the development of density functional theory methods, e.g., the investigation of the delocalization error. This delocalization error causes the dependence of the energy on the number of electrons (N) to deviate from its exact piecewise linear behavior, an error which is the basis of many well-known limitations of commonly used density-functional approximations (DFAs). Following our previous work on the analytical hardness η± for pure functionals, we extend its application to hybrid and range-separated functionals. A comparison is made between the analytical hardness and the slope of the delocalization function introduced by Hait and Head-Gordon. Our results show that there is a linear relationship between its slope and the analytical hardness. An approximate scheme is presented to construct the energy vs N curve without fractional occupation number calculations. The extension to densities is discussed.

概念密度泛函理论(CDFT)已经超越了其在阐明化学反应性方面的传统作用,扩展到密度泛函理论方法的发展,例如对脱域误差的研究。这种脱域误差会导致能量对电子数(N)的依赖性偏离其精确的片断线性行为,这种误差是常用密度泛函近似(DFA)的许多众所周知的局限性的基础。继我们之前研究纯函数的分析硬度 η± 之后,我们将其应用扩展到混合函数和范围分离函数。我们将分析硬度与海特和海德-戈登引入的脱域函数斜率进行了比较。结果表明,其斜率与分析硬度之间存在线性关系。我们还提出了一种近似方案,无需计算分数占位数即可构建能量与 N 的关系曲线。我们还讨论了向密度的扩展。
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引用次数: 0
Unusual and Persistent Free Radical Intermediate Production from 2-Pyridyl Ketones via UV Irradiation: A Direct ESR Study. 通过紫外线辐照从 2-Pyridyl Ketones 生成异常而持久的自由基中间体:直接 ESR 研究。
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-11-05 DOI: 10.1021/acs.jpclett.4c02657
Lin-Na Xie, Chun-Hua Huang, Dan Xu, Zhen-Huan Li, Li Qin, Bo Shao, Li Mao, Jie Shao, Zhi-Sheng Liu, Jing Chen, Zhi-Guo Sheng, Zhi-Hui Zhang, Ben-Zhan Zhu

Aryl ketones are often used as photosensitizers and photoinitiators. Free radical intermediates have been suggested, but not confirmed, to be generated after photoirradiation. Here we found, unexpectedly, that a persistent radical was produced from di-2-pyridyl ketone after UV irradiation, which was detected by the direct ESR method. Interestingly, the persistent radical was very sensitive to oxygen and the pH of the reaction medium. A similar persistent radical was also observed from phenyl-2-pyridyl ketone, but not from 3-benzoylpyridine, 4-benzoylpyridine, and benzophenone, suggesting that the presence of a carbonyl group connected to the ortho-position of the pyridine ring is critical for such radical production. By complementary applications of ESR, HPLC, and ESI-Q-TOF-MS, the possible chemical structures of the persistent radical and final product were identified, and the possible underlying reaction mechanism was proposed. This represents the first report on UV-induced persistent radical generation from 2-pyridyl ketones, which should be of great significance for future studies.

芳基酮经常被用作光敏剂和光引发剂。有人认为光照射后会产生自由基中间体,但尚未得到证实。在这里,我们意外地发现,在紫外线照射后,二-2-吡啶基酮产生了一种持久自由基,并通过直接 ESR 方法检测到了这种自由基。有趣的是,这种持久自由基对氧气和反应介质的 pH 值非常敏感。从苯基-2-吡啶基酮中也观察到了类似的持久自由基,但从 3-苯甲酰基吡啶、4-苯甲酰基吡啶和二苯甲酮中没有观察到。通过 ESR、HPLC 和 ESI-Q-TOF-MS 的互补应用,确定了持久自由基和最终产物的可能化学结构,并提出了可能的基本反应机制。这是首次报道紫外线诱导 2-吡啶基酮生成持久自由基,对今后的研究具有重要意义。
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引用次数: 0
Comment on “Localized and Delocalized States of a Diamine Cation: Resolution of a Controversy” 评论 "二胺阳离子的局部和非局部状态:争议的解决"
IF 6.475 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 DOI: 10.1021/acs.jpclett.4c01984
Gabriel S. Phun, Bryan M. Wong
Since its appearance in [Cheng, X.; Zhang, Y.; Jónsson,E.; Jónsson, H.; Weber, P. M. Nat. Commun. 2016, 7, 11013] and recent re-investigation in [Gałyńska,M.; Ásgeirsson, V.; Jónsson, H.; Bjornsson, R. J. Phys. Chem. Lett., 2021, 12, 1250−1255], the dimethylpiperazine cation (DMP+) has generated considerable discussion and controversy in the scientific literature over the existence of stable, local energy minima in this molecular system. Specifically, prior assumptions that the Rydberg state and radical cation of DMP are similar have led to significant confusion and debate regarding the accuracy of various quantum chemistry methods and the existence of stable configurations of DMP+ itself. The purpose of this Viewpoint is to highlight recent studies that call into question the main findings in the previously mentioned works as well as present new CCSDT (Coupled-Cluster with Single, Double, and Triple excitations) calculations to finally bring closure to this controversy.
自从它出现在 [Cheng, X.; Zhang, Y.; Jónsson,E.; Jónsson, H.; Weber, P. M. Nat.Nat.2016, 7, 11013] 以及最近在 [Gałyńska,M.; Ásgeirsson, V.; Jónsson, H.; Bjornsson, R. J. Phys. Chem.Lett., 2021, 12, 1250-1255],二甲基哌嗪阳离子 (DMP+) 在科学文献中引起了关于该分子体系是否存在稳定的局部能量极小值的大量讨论和争议。具体来说,之前关于 DMP 的雷德贝格态和自由基阳离子相似的假设,导致了关于各种量子化学方法的准确性以及 DMP+ 本身是否存在稳定构型的严重混淆和争论。本 "视点 "旨在重点介绍最近的研究,这些研究对之前提到的著作中的主要发现提出了质疑,并介绍了新的 CCSDT(具有单、双和三重激发的耦合簇)计算,最终结束了这场争论。
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引用次数: 0
Assessing the Influence of Illumination on Ion Conductivity in Perovskite Solar Cells. 评估照明对 Perovskite 太阳能电池离子传导性的影响。
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-11-03 DOI: 10.1021/acs.jpclett.4c02403
Andreas Schiller, Sandra Jenatsch, Balthasar Blülle, Miguel Angel Torre Cachafeiro, Firouzeh Ebadi, Nasim Kabir, Mostafa Othman, Christian Michael Wolff, Aïcha Hessler-Wyser, Christophe Ballif, Wolfgang Tress, Beat Ruhstaller

Whether illumination influences the ion conductivity in lead-halide perovskite solar cells containing iodide halides has been an ongoing debate. Experiments to elucidate the presence of a photoconductive effect require special devices or measurement techniques and neglect possible influences of the enhanced electronic charge concentrations. Here, we assess the electronic-ionic charge transport using drift-diffusion simulations and show that the well-known increase in capacitance at low frequencies under illumination is caused by electronic currents that are amplified due to the screening of the alternating electric field by the ions. We propose a novel characterization technique to detect a potential photoinduced increase in ionic conductivity based on capacitance measurements on fully integrated devices. The method is applied to a range of perovskite solar cells with different active layer materials. Remarkably, all measured samples show a clear signature of photoenhanced ion conductivity, posing fundamental questions on the underlying nature of the photosensitive mechanism.

照明是否会影响含有碘化物卤化物的铅-卤化物包晶太阳能电池中的离子导电性一直是一个争论不休的问题。阐明光电导效应的实验需要特殊的设备或测量技术,并且忽略了电子电荷浓度增强可能带来的影响。在此,我们利用漂移扩散模拟对电子-离子电荷传输进行了评估,结果表明,众所周知的照明下低频电容的增加是由电子电流引起的,而电子电流由于离子对交变电场的屏蔽而被放大。我们提出了一种新颖的表征技术,可根据全集成器件的电容测量结果,检测潜在的光诱导离子电导率增加。该方法适用于一系列具有不同活性层材料的过氧化物太阳能电池。值得注意的是,所有测量样品都显示出明显的光增强离子电导率特征,从而提出了有关光敏机制基本性质的基本问题。
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引用次数: 0
Ultrafast Spectroscopic Investigation of the Aggregation Induced TADF from High-Level Reversed Intersystem Crossing 高水平反向系统间交叉聚合诱导 TADF 的超快光谱研究
IF 6.475 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 DOI: 10.1021/acs.jpclett.4c02395
Ziqi Deng, Yunfeng Luo, Guanheng Huang, Jiaxing He, David Lee Phillips
The thermally activated delayed fluorescence (TADF) originating from high-level intersystem crossing (hRISC) presents great potential in realizing a more full utilization of triplet excitons. In this study, DPA-FBP and TPA-FBP were doped in a PMMA film with different weight fractions to study the effect of aggregation on the luminescence properties. As a result, the TADF feature from hRISC was only found in the 50 wt % doped film, whereas the 1 wt % doped film only shows prompt fluorescence. The fs-TA spectroscopy results reveal that the 50 wt % film will generate charge transfer species to lower the energy gap, so that the high-lying triplet exciton can transition back to the singlet state, whereas that of the 1 wt % film will quickly transition to the lowest triplet state due to the unfavorable energy splitting. This study provides a new insight into aggregation effects on the excited-state properties of hot exciton materials and the solid-state photodynamic.
源于高水平系统间交叉(hRISC)的热激活延迟荧光(TADF)在更充分地利用三重激子方面具有巨大潜力。本研究在 PMMA 薄膜中掺入了不同重量分数的 DPA-FBP 和 TPA-FBP,以研究聚集对发光特性的影响。结果发现,只有在掺杂 50 重量百分比的薄膜中才会出现来自 hRISC 的 TADF 特征,而掺杂 1 重量百分比的薄膜则只显示出瞬时荧光。fs-TA光谱结果表明,50 wt %薄膜会产生电荷转移物种以降低能隙,从而使高位三重态激子过渡回单重态,而 1 wt % 薄膜中的三重态激子则会因不利的能量分裂而迅速过渡到最低的三重态。这项研究为聚合效应对热激子材料激发态特性和固态光动力学的影响提供了新的见解。
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引用次数: 0
Wave Function Localization Reduces the Bandgap of Disordered Double Perovskite Cs2AgBiBr6. 波函数局部化降低了无序双包晶石 Cs2AgBiBr6 的带隙。
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-11-04 DOI: 10.1021/acs.jpclett.4c02946
Dongyu Liu, Bayan Amer Abzakh, Elena A Kazakova, Dmitrii A Abrameshin, Pavel A Troshin, Run Long, Andrey S Vasenko

Double perovskite Cs2AgBiBr6 is a promising alternative to lead-based perovskites with excellent stability and attractive optoelectronic properties. However, a relatively large bandgap severely limits its performance in many applications such as solar cells and photodetectors. It has been reported that a random distribution of Ag and Bi atoms in Cs2AgBiBr6 effectively reduces its bandgap without introducing dopants or impurities, while the mechanism remains unclear. Here, using density functional theory calculations, we demonstrate that the Ag-Bi disorder in Cs2AgBiBr6 generates localized electronic states as band edges to regulate the bandgap. The disordered structures segregate Ag and Bi atoms in the lattice, and the formed homoatomic clusters lead to wave function localization. Moreover, the bandgap decrease exhibits a non-monotonic dependence on the degree of disorder. Our results are comparable with experimental observations and provide crucial insights into understanding the order-disorder transition in double perovskites.

双包晶石 Cs2AgBiBr6 具有出色的稳定性和诱人的光电特性,是铅基包晶石的理想替代品。然而,相对较大的带隙严重限制了它在太阳能电池和光电探测器等许多应用中的性能。据报道,Cs2AgBiBr6 中银原子和铋原子的随机分布可在不引入掺杂剂或杂质的情况下有效降低其带隙,但其机理仍不清楚。在这里,我们利用密度泛函理论计算证明,Cs2AgBiBr6 中的银铋无序结构会产生局部电子态,作为带边来调节带隙。无序结构在晶格中分离了 Ag 原子和 Bi 原子,形成的同原子团簇导致了波函数的局部化。此外,带隙的减小与无序程度呈非单调依赖关系。我们的研究结果与实验观察结果相当,为理解双包晶的有序-无序转变提供了重要见解。
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引用次数: 0
Luminescence and Transport Behavior in Incommensurately Modulated CaGd2(MoO4)4:Yb/Er. 不可比调制 CaGd2(MoO4)4:Yb/Er.中的发光和传输行为
IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL Pub Date : 2024-11-14 Epub Date: 2024-11-06 DOI: 10.1021/acs.jpclett.4c02554
Yinghan Wang, Zeyue Zhang, Guohong Cai, Jingxie Xiong, Zhengren Tao, Chunhai Wang, Junliang Sun, Shi Ye

The phenomenon of thermal quenching of luminescence can significantly compromise the efficiency of luminescent materials, a process accompanied by the generation of substantial phonon populations. While plenty of models for elucidating this behavior have been proposed, the crucial role of phonon transport has largely been neglected, particularly in the enigmatic incommensurate scheelite structure with good luminescence performance. In this study, we delve into the thermal quenching dynamics of the near-infrared emission in the incommensurately modulated CaGd2(MoO4)4:Yb/Er system. Our comprehensive investigation reveals distinct evolutionary patterns in electrical conductivity, luminescence intensity, thermal conductivity, and Raman scattering at varying temperature regimes. Notably, we have determined that thermally induced ion migration, occurring above ∼300 °C, serves as a pivotal trigger for the activation of all phonons and the enhancement of phonon-defect scattering within this incommensurate framework. This phenomenon not only diminishes the thermal conductivity but also accelerates the multiphonon relaxation of the Er3+ emission levels, culminating in a marked thermal quenching of luminescence. This work illuminates the thermal quenching mechanism of luminescence by focusing on phonon scattering dynamics, providing critical insights for the design of thermally robust near-infrared luminescent materials, which are essential for the advancement of optical amplification systems.

发光的热淬灭现象会严重影响发光材料的效率,这一过程伴随着大量声子群的产生。虽然已经提出了大量模型来阐明这种行为,但声子输运的关键作用在很大程度上被忽视了,尤其是在具有良好发光性能的神秘不互变白钨矿结构中。在本研究中,我们深入研究了非共相调制 CaGd2(MoO4)4:Yb/Er 体系中近红外发射的热淬灭动力学。我们的全面研究揭示了不同温度条件下导电性、发光强度、热导率和拉曼散射的不同演化模式。值得注意的是,我们已经确定,发生在 ∼300 °C以上的热诱导离子迁移是激活所有声子的关键触发器,并增强了这种不相称框架内的声子-缺陷散射。这种现象不仅降低了热导率,还加速了 Er3+ 发射水平的多声子弛豫,最终导致发光的明显热淬灭。这项研究通过关注声子散射动力学,阐明了发光的热淬灭机制,为设计热稳定性近红外发光材料提供了重要的启示,这对于光学放大系统的发展至关重要。
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引用次数: 0
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