Effects of 5f-elements on electronic structures and spectroscopic properties of gold superatom model

5f-elements encaged in a gold superatomic cluster are capable of giving rise to unique optical properties due to their hyperactive valence electrons and great radial components of 5f/6d orbitals. Herein, we review our first-principles studies on electronic structures and spectroscopic properties of a series of actinide-embedded gold superatomic clusters with different dimensions. The three-dimensional（3D） and two-dimensional（2D） superatom clusters possess the 18-electron configuration of 1S21P61D10 and 10-electron configuration of 1S21P41D4, respectively. Importantly, their electronic absorption spectra can also be effectively explained by the superatom orbitals. Specifically, the charge transfer（CT） transitions involved in surface-enhance Raman spectroscopy（SERS） spectra for 3D and 2D structures are both from the filled 1D orbitals, providing the enhancement factors of the order of ～ 10^4 at 488 nm and ～ 10^5 at 456 nm, respectively. This work implies that the superatomic orbital transitions involved in 5f-elements can not only lead to a remarkable spectroscopic performance, but also a new direction for optical design in the future.

Bottom-up design and assembly with superatomic building blocks

Constructing specific structures from the bottom up with artificial units is an important interdisciplinary topic involving physics,chemistry,materials,and so on.In this work,we theoretically demonstrated the feasibility of using superatoms as building blocks to assemble a complex at atomic-level precision.By using a series of actinide-based endohedral metallofullerene(EMF)superatoms that can form one,two,three and four chemical bonds,a planar complex with intra-and inter-molecular interactions was assembled on the Au(111)surface.This complex is composed of two parts,containing ten and eight superatoms,respectively.The electronic structure analysis shows that the electron density inside each part is connected and the closed-shell electronic arrangement system is designed.There is also an obvious van der Waals boundary by physical adsorption between the two parts,and a stable complex is formed.Since this complex is realized by the first-principles calculations of quantum mechanics,our results help not only achieve atomic-level precision construction with artificial superatomic units but also maintain atomic-level functional properties.

How ligand coordination and superatomic-states accommodate the structure and property of a metal cluster:Cu_(4)(dppy)_(4)Cl_(2)vs.Cu_(21)(dppy)_(10)with altered photoluminescence

We have synthesized two copper nanoclusters(NCs)with a protection of the same ligand diphenylphosphino-2-pyridine(C_(17)H_(14)NP,dppy for short),formulated as Cu_(4)(dppy)_(4)Cl_(2)and Cu21(dppy)10,respectively.The former one bears a distorted tetrahedron Cu4 core with its six edges fully protected by chlorine and dppy ligands,while the latter presents a symmetric Cu_(21)core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination.Interestingly,the Cu_(4)(dppy)_(4)Cl_(2)cluster exhibits a strong yellow emission at∼577 nm,while Cu_(21)(dppy)_(10)displays dual emissions in purple(∼368 nm)and green(∼516 nm)regions respectively.In combination with TD-DFT calculations,we demonstrate the origin of altered emissions and unique stability of the two copper nanoclusters pertaining to the ligand coordination and metallic superatomic states.

Designing topological and correlated 2D magnetic states via superatomic lattice constructions of zirconium dichloride

Magnetic materials could realize the intriguing quantum anomalous Hall effect and metal-to-insulator transition when combined with band topology or electronic correlation,which have broad prospects in quantum information,spintronics,and valleytronics.Here,we propose the approach of designing novel two-dimensional(2D)magnetic states via d-orbital-based superatomic lattices.Specifically,we chose triangular zirconium dichloride disks as superatoms to construct the honeycomb superatomic lattices.Using first-principles calculations,we identified a series of 2D magnetic states with varying sizes of superatoms.We found the non-uniform stoichiometries and geometric effect of superatomic lattice give rise to spin-polarized charges arranged in different magnetic configurations,containing ferromagnetic coloring triangles,antiferromagnetic honeycomb,and ferromagnetic kagome lattices.Attractively,these magnetic states are endowed with nontrivial band topology or strong correlation,forming an ideal Chern insulator or antiferromagnetic Dirac Mott insulator.Our work not only reveals the potential of d-orbital-based superatoms for generating unusual magnetic configurations,but also supplies a new avenue for material engineering at the nanoscale.

Organic ligand mediated evolution from superalkalis to superatomic molecules and nanowires

Superatoms are considered as promising building blocks for customizing superatomic molecules and cluster-assembly nanomaterials due to their tunable electronic structures and functionalities.Electron counting rules,which mainly adjust the shell-filling of clusters,are classical strategies in designing superatoms.Here,by employing the density functional theory(DFT)calculations,we proved that the 1,4-phenylene diisocyanide(CNC_(6)H_(4)NC)ligand could dramatically reduce the adiabatic ionization potentials(AlPs)of the aluminum-based clusters,which have 39,40,and 41 valence electrons,respectively,to give rise to superalkali species without changing their shell-filling.Moreover,the rigid structure of the ligand can be used as a bridge firmly linking the same or different aluminum-based clusters to form superatomic molecules and nanowires.In particular,the bridging process was observed to enhance their nonlinear optical(NLO)responses,which can be further promoted by the oriented external electric field(OEEF).Also,the stable cluster-assembly XAl_(12)(CNC_(6)H_(4)NC)(X=Al,C,and P)nanowires were constructed,which exhibit strong absorption in the visible light region.These findings not only suggest an effective ligand-field strategy in superatom design but also unveil the geometrical and electronic evolution from the CNC_(6)H_(4)NC-based superatoms to superatomic molecules and nanomaterials.

Ligand accommodation causes altered reactivity of silver clusters with iodomethane:superatomic stability of Ag_(9)I_(2)^(+)in mimicking XeF_(2)

Exploring metal cluster reactivity with alkyl halides enables to understand the related chemical mechanism of metal surfaces in terms of active sites.Here we report a study of Ag_(n)^(+)(n=1-27)clusters reacting with iodomethane by a flow tube apparatus in tandem with a customized triple quadrupole mass spectrometer.Strong even/odd alternation of the Ag_(n)^(+)is observed in their reactions with CH_(3)I,where silver clusters with even-number,Ag_(2n)^(+),find favorable products of Ag_(2n)I_(1,3)^(+)series,while the Ag_(2n−1)^(+)clusters form Ag_(2n−1)I_(2,4)^(+)products.Interestingly,Ag_(9)^(+)shows up with prominent mass abundance but allows for the formation of Ag_(9)I_(2)^(+),which finds an echo with the formation of Ag_(10)I_(3)^(+).We illustrate the enhanced stability of Ag_(9)I_(2)^(+)and Ag_(10)I_(3)^(+)by showing their significantly enlarged highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)gaps and balanced charge distribution compared with the bare metal clusters,respectively.Also elucidated,is the superatomic nature of these bare and iodinated silver clusters,especially Ag_(9)I_(2)^(+)which mimics the rare-gas compound XeF_(2).This study expands a vivid example of special and general superatoms,and enriches the general knowledge on how a ligand stabilizes a metal cluster.

Direct assembly between closed-shell coinage metal superatoms

Bottom-up constructing all-metal functional materials is challenging,because the metal clusters are prone to lose their original structures during coalensence.In this work,we report that closed-shell coinage metal superatoms can achieve direct chemical bonding without losing their electronic properties.The reason is that the supermolecule formed by two superatoms has the same number of bonding and anti-bonding supermolecular orbitals,in which the bonding orbitals contribute to bonding and the antibonding orbitals with anti-phase orbitals delocalized over each monomer to maintain the individual geometric and electronic structural properties.Further analysis indicates the interactions between two superatoms are too weak to break the structure of monomers,which is confirmed by the first-principles molecular dynamics simulations.With these superatoms as the basic units,a series of robust one-dimensional and two-dimensional nanostructures are fabricated.Our findings provide a general strategy to take advantage of superatoms in regulating bonding compared to natural atoms,which paves the way for the bottom-up design of materials with collective properties.

Chlorine-passivated superatom Al37clusters for nonlinear optics

Utilizing a facile top-down synthetic procedure, here we report the finding of a chlorine-passivated Al_(37) superatom cluster. It is demonstrated that the presence of electrophilic groups, severing as protecting ligands, alters the valence electron count of the metallic core and stabilize the as-prepared aluminum clusters especially when even-numbered chlorine atoms are located at equilibrium positions. Following the discussion regarding their reasonable stabilities, we illustrate the feasible reaction pathways in forming such chlorine-passivated Al_(37) superatom clusters which bear delocalized superatomic orbitals with five valence 3P^5 electrons shifting to the chlorine ligands indicative of a closed electron shell 2F^(14) of the metal core. The successful synthesis of such chlorine-protected aluminum clusters evidences the compatibility of general theory of cluster chemistry in both gas phase and wet chemistry. Such simple-ligand-protected aluminum clusters exhibit reverse-saturated-absorption(RSA) nonlinear optical property pertaining to electronic transitions within the discrete energy states of cluster materials.

Actinide-embedded gold superatom models： Electronic structure, spectroscopic properties, and applications in surface-enhanced Raman scattering

Actinide elements encaged in a superatomic cluster can exhibit unique properties due to their hyperactive valence electrons. Herein, the electronic and spectroscopic properties of Th@Au14 are predicted and compared with that of the isoelectronic entities [Ac@Au14]- and [Pa@Au14]＋ using density functional theory. The calculation results indicate that these clusters all adopt a closed- shell superatomic 18-electron configuration of the 1S21p61D10 Jellium state. The absorption spectrum of Th@Au14 can be interpreted by the Jelliumatic orbital model. In addition, calculated spectra of pyridine-Th@Au14 complexes in the blue laser band exhibit strong peaks attributable to charge transfer （CT） from the metal to the pyridine molecule. These charge-transfer bands lead to a resonant surface-enhanced Raman scattering （SERS） enhancement of -104. This work suggests a basis for designing and synthesizing SERS substrate materials based on actinide-embedded gold superatom models.

B_(111),B_(112),_(B113),and B_(114):The most stable core-shell borospherenes with an icosahedral B_(12) core at the center exhibiting superatomic behaviors

Boron allotropes are known to be predominately constructed by icosahedral B_(12) cages,while icosahedral-B_(12) stuffing proves to effectively improve the stability of fullerene-like boron nanoclusters in the size range between B_(98)–B_(102).However,the thermodynamically most stable core-shell borospherenes with a B_(12) icosahedron at the center still remains unknown.Based on the structural motif of D5h C_(70) and extensive first-principles theory calculations,we predict herein the high-symmetry C5v B111+(3)which satisfies the Wade’s n+1 and n+2 skeletal electron counting rules exactly and the approximately electron sufficient Cs B_(111)(4),Cs B_(112)(5),Cs B_(113)(6),and Cs B_(114)(7)which are the most stable neutral core-shell borospherenes with a B_(12) icosahedron at the center reported to date in the size range between B_(68)–B_(130),with Cs B112(5)being the thermodynamically most favorite species in the series.Detailed orbital and bonding analyses indicate that these spherically aromatic species all contain a negatively charged icosahedral B_(122)−core at the center which exhibits typical superatomic behaviors in the electronic configuration of 1S21P61D101F8,with its dangling valences saturated by twelve radial B-B 2c-2eσbonds between the B_(12) inner core and the B_(70) outer shell.The infrared(IR)and Raman spectra of the concerned species are computationally simulated to facilitate their future characterizations.

Evolution of all-carboxylate-protected superatomic Ag clusters confined in Ti-organic cages

In this study,the size of the titanium organic cage was controlled to achieve the restricted growth from a single Ag(I)atom(Ag@Ti_(5))to rare all-carboxylate-protected superatomic Ag cluster(Ag6@Ti_(6)).The classical octahedral Ag_(6)^(4+) cluster with two delocalized electrons(2e)has been encapsulated in a Ti6 organic cage,which shows high stability in air and dimethyformamide(DMF).Furthermore,larger 2e nested double-tetrahedra Ag clusters(Ag_(8)^(6+) and Ag_(9)^(7+))protected using a tetrahedral hollow metalloligand framework(Ag_(8)@Ti_(4) and Ag_(9)@Ti_(4))were obtained.Electrospray ionization mass spectrometry(ESI-MS)and density functional theory(DFT)calculations confirmed that there are two delocalized electrons on these small Ag clusters.This study provides a new form of protection for superatomic Ag clusters and provides a feasible strategy for the development of stable Ag clusters.

Layer-by-layer alloying of NIR-Ⅱ emissive M50(Au/Ag/Cu)superatomic nanocluster

The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has long been a challenging pursuit.In this work,two novel alloy nanoclusters[PPh_(4)]_(4)[Ag_(32)Cu_(18)(PFBT)_(36)]((AgCu)_(50))and[PPh_(4)]_(4)[Au_(12)Ag_(20)Cu_(18)(PFBT)_(36)](Au_(12)(AgCu)_(38)),where PFBT is pentafluorobenzenethiolate,with shell-by-shell configuration of M_(12)@Ag_(20)@Cu_(18)(PFBT)_(36)(M=Ag/Au)were synthesized by a facile one-pot co-reduction method.Notably,a fingerprint library of[Ag_(50)−xCux(PFBT)_(36)]^(4−)(x=0 to 50)from Ag_(50)to Cu_(50)has been successfully established as revealed by electrospray ionization mass spectrometry.Single-crystal X-ray diffraction analysis of trimetallic Au_(12)(AgCu)_(38)confirmed the layer-by-layer alloying under reducing conditions.What is more,(AgCu)_(50)and Au12(AgCu)_(38)both show broad photoluminescence(PL)peak in the second near-infrared(NIR-II)window,and the Au doping in the innermost shell considerably enhances the photoluminescence intensity.This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.

Superatomic Signature and Reactivity of Silver Clusters with Oxygen:Double Magic Ag_(17)^– with Geometric and Electronic Shell Closure

Understanding the stability and reactivity of silver clusters toward oxygen provides insights to design new materials of coinage metals with atomic precision.Herein,we report a systematic study on anionic silver clusters,Ag_(n)^(−)(n=10-34),by reacting them with O_(2) under multiple-collision conditions.Mass spectrometry observation presents the odd-even alternation effect on the reaction rates of these Agn−clusters.

超级里德伯原子间的稳态关联集体激发与量子纠缠

处于同一偶极阻塞区域的里德伯原子系综可以看作一个超级原子,如果它们被捕获在两个不同的光偶极阱中,那么每一个光偶极阱中的子原子系综可以看作为一个亚超级原子.由于这两个亚超级原子共享不超过一个激发的里德伯原子,所以它们会强烈地关联起来.本文研究这两个里德伯亚超级原子的稳态关联集体激发特性和量子纠缠行为.结果表明原子数目带来的影响非常明显:里德伯亚超级原子越大(包含原子数目越多),集体激发概率越大;最大纠缠只发生在等大的两个里德伯亚超级原子之间.通过增加原子数目,可以实现介观领域的量子纠缠,对量子-经典对应的研究以及量子信息处理有着重要的作用.

二十面体Np@Al1_(2)团簇的电子和磁性质

一个长期争论的系统包含锕系元素是定位的程度和参与化学键的5f轨道在锕系系列。本文用密度泛函理论说明了Np的5f轨道在超原子成键中具有双重性;部分5f电子表现出巡游性参与成键,部分5f电子表现出局域性显示磁矩。这项工作不仅为磁性超原子的培育提供了新的配方,而且对超导材料和重费米子系统的设计也很有借鉴作用。

上连通和超连通六次点传递图(英文)

图G称为上连通的,若对每个最小割集C,G-C有孤立点.G称为超连通的,若对每个最小割集C,G-C恰有两个连通分支,且其中之一为孤立点.本文刻画了上连通或超连通六次点传递图.

从原子到超原子的原子层次新机遇

为何超原子如此重要?从发展过程来体会,是因为终于可以把纷繁复杂的团簇结构以量子力学属性实现物理规律把握,从而为以团簇作为基元的物性表征与调控包括相关的制造和功能应用提供了基于原子层次的抓手.因此可认为,由团簇科技发展到超原子的物理学研究是必然的,所以我们提出了超原子物理学的概念和范畴.超原子作为归属于分子的多原子复杂系统,它的电子结构与原子有相近性,凸显了超原子系统中相互作用有深刻且丰富的物理内涵.依托于原子物理学的巨大成就,将原子层次的科技能力结合到超原子研究上,将开辟新的领域方向,促进从结构出发的传统研究思路转变到以功能为核心的研究范式,从而带来新的发展机遇.

里德伯电磁感应透明中的相位

本文在典型的里德伯电磁感应透明系统中研究弱探测场在相互作用原子系统中的传播特性,重点关注基于偶极阻塞效应的探测场相位的合作光学非线性行为.通过与探测场透射率和光子关联作对比,发现相位的光学响应具有新特性:共振和Autler-Townes劈裂条件下相位对入射场强和初始光子关联不敏感,而在两者之间的频率范围内相位响应具有非线性特征,尤其在经典光频率处最显著.此外,提高主量子数和原子密度都会促进相位的非线性效应.综上,与探测场透射率和光子关联一样,相位可以作为合作光学非线性的另一个标识来刻画非线性现象,对里德伯电磁感应透明研究是一个有力的补充.

超原子及其组装材料

近年来,在团簇物理学中出现了超原子这一新兴研究方向。本文结合超原子已有的实验和理论研究,简单介绍了超原子概念及其发展历程,论述了超原子研究的范畴、目的和意义,分析了超原子及其组装材料的研究现状及潜在研究课题。