High-throughput identification of one-dimensional atomic wires and first principles calculations of their electronic states

Low dimensional materials are suitable candidates applying in next-generation high-performance electronic,optoelectronic,and energy storage devices because of their uniquely physical and chemical properties.In particular,one-dimensional(1D)atomic wires(AWs)exfoliating from 1D van der Waals(vdW)bulks are more promising in next generation nanometer(nm)even sub-nm device applications owing to their width of few-atoms scale and free dandling bonds states.Although several 1D AWs have been experimentally prepared,few 1D AW candidates could be practically applied in devices owing to lack of enough suitable 1D AWs.Herein,367 kinds of 1D AWs have been screened and the corresponding computational database including structures,electronic structures,magnetic states,and stabilities of these 1D AWs has been organized and established.Among these systems,unary and binary 1D AWs with relatively small exfoliation energy are thermodynamically stable and theoretically feasible to be exfoliated.More significantly,rich quantum states emerge,such as 1D semiconductors,1D metals,1D semimetals,and 1D magnetism.This database will offer an ideal platform to further explore exotic quantum states and exploit practical device applications using 1D materials.The database are openly available at http://www.dx.doi.org/10.11922/sciencedb.j00113.00004.

Syntheses of molecular wires containing redox center:Reversible redox property and good energy level matching with Au electrode

Molecular wires with tetrathiafulvalene （TTF） as redox center were synthesized and characterized. UV-vis spectra and cyclic voltammetry showed these wires had good reversible redox behavior under ambient conditions and their HOMO energy levels （--5.0 eV） matched well with the Fermi level of Au （--5.1 eV）.

Lead-free molecular one-dimensional perovskite for efficient X-ray detection

In recent years,great progress has been achieved for organicinorganic halide perovskites due to their excellent optoelectronic properties and stability for photovoltaics,light emitting diodes,and high-energy radiation detection[1-5].One-dimensional(1D)perovskites,as an important derivative of three-dimensional(3D)perovskites,exhibit low exciton dissociation efficiency,which can produce strong quantum confinement and form self-trapping excited state[6],In addition,the hydrophobic properties and the inhibition of ion migration from large organic cations improve the moisture and thermal stability for optoelectronic devices.

Fabrication of Two-dimensional Monolayer and One-dimensional Wire of Zn-tetra-[3,5-di-t-butylphenyl]-porphyrin on Cu(100) Surface

We describe in this paper the fabrication of two- and one-dimensional nanostructures with organic molecular beam epitaxy （OMBE） principle based on controlled selfassembly by using adsorbate-substrate and intennolecular interactions that are important in molecular fabrication. Cu（100） single crystal was used as substrate in fabricating molecular nanostructures. Scanning tunneling microscopy （STM） experiments confirmed that Zn-tetra- [3,5-di-t-butylphenyl]porphyrin-molecules can be used to fabricate both monolayer and molecular wire on Cu（100） surface simultaneously, and the latter is arranged on the terrace edges. We herein briefly discuss the selectivity in terms of a mechanism in which the highest occupied and lowest unoccupied molecular orbitals （HOMO and LUMO） of the molecules interact with the surface.

A Rapid Solid-phase Synthesis to Soluble Oligothiophene Molecular Wires

A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity.

Current–Voltage Characteristics of the Aziridine-Based Nano-Molecular Wires: a Light-Driven Molecular Switch

Using nonequilibrium Green＇s function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-（4-nitrophenyl）-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y（111）（Y =Au, Ag and Pt） on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state（low resistance switches to high resistance）. Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.

Cyanopolyynes as Organic Molecular Wires in the Interstellar Medium

Cyanopolyynes (H[C≡C]n-CN or HC2n+1N, where n = 1, 2, 3, …, n) are commonly observed in the interstellar medium (ISM) as well as in the envelopes of carbon-rich stars. These linear molecular structures can be well described with a one-dimensional conduction model, which considers the scattering processes of electrons through the charge transfer conduction bridge of the H[C≡C]n-molecular wire containing the CN group as an electron-acceptor terminal unit. Therefore, our results using this model enable a better understanding of the longest molecules observed in interstellar space and provide new insight into why these particular cyanopolyynes reach a maximum length, such as is observed from astronomical experimental spectral data and cosmological chemical models. Dipole moments and geometrical parameters of these cyanopolyynes were obtained from ab initio molecular orbital calculations using the restricted Hartree-Fock approach and 6-311G* basis set, in order to obtain the inner resistance as a new parameter of chemical reaction feasibility for this molecular series. Using this last molecular parameter, we have been able to analyze the possibility of identifying long molecular species that can be found under local thermodynamic equilibrium in some ISM such us HC25H, HC27H, and HC29N, which have not been observed at present.

Mechanism of microweld formation and breakage during Cu-Cu wire bonding investigated by molecular dynamics simulation

Currently,wire bonding is the most popular first-level interconnection technology used between the die and package terminals,but even with its long-term and excessive usage,the mechanism of wire bonding has not been completely evaluated.Therefore,fundamental research is still needed.In this study,the mechanism of microweld formation and breakage during Cu-Cu wire bonding was investigated by using molecular dynamics simulation.The contact model for the nanoindentation process between the wire and substrate was developed to simulate the contact process of the Cu wire and Cu substrate.Elastic contact and plastic instability were investigated through the loading and unloading processes.Moreover,the evolution of the indentation morphology and distributions of the atomic stress were also investigated.It was shown that the loading and unloading curves do not coincide,and the unloading curve exhibited hysteresis.For the substrate,in the loading process,the main force changed from attractive to repulsive.The maximum von Mises stress increased and shifted from the center toward the edge of the contact area.During the unloading process,the main force changed from repulsive to attractive.The Mises stress reduced first and then increased.Stress concentration occurs around dislocations in the middle area of the Cu wire.

Influence of InAs deposition thickness on the structural and optical properties of InAs quantum wires

The influence of InAs deposition thickness on the structural and optical properties of InAs/InA1As quantum wires （QWR） superlattices （SLS） was studied. The transmission electron microscopy （TEM） results show that with increasing the InAs deposited thickness, the size uniformity and spatial ordering of InAs QWR SLS was greatly improved, but threading dislocations initiated from InAs nanowires for the sample with 6 monolayers （MLs） InAs deposition. In addition, the zig-zag features along the extending direc- tion and lateral interlink of InAs nanowires were also observed. The InAs nanowires, especially for the first period, were laterally compact. These structural features may result in easy tunneling and coupling of charge carders between InAs nanowires and will hamper their device applications to some extent. Some suggestions are put forward for further improving the uniformity of the stacked InAs QWRs, and for suppressing the formation of the threading dislocations in InAs QWR SLS.

Mobility limited by cluster scattering in ternary alloy quantum wires

The mobility limited by cluster scattering in ternary alloy semiconductor quantum wire （QWR） is theoretically inves- tigated under Born approximation. We calculate the screened mobility due to clusters （high indium composition lnGaN） scattering in the InxGal_xN QWR structure. The characteristics of the cluster scattering mechanism are discussed in terms of the indium composition of clusters, the one-dimensional electron gas （1DEG） concentration, and the radius of QWR. We find that the density, breadth of cluster, and the correlation length have a strong effect on the electron mobility due to cluster scattering, Finally, a comparison of the cluster scattering is made with the alloy-disorder scattering. It is found that the cluster scattering acts as a significant scattering event to impact the resultant electron mobility in ternary alloy QWR.

Advances in Molecular Electronics:A Brief Review

The field of molecular electronics,also known as moletronics,deals with the assembly of molecular electronic components using molecules as the building blocks.It is an interdisciplinary field that includes physics,chemistry,materials science,and engineering.Moletronics mainly deals with the reduction of size of silicon components.Novel research has been performed in developing electrical-equivalent molecular components.Moletronics has established its influence in electronic and photonic applications,such as conducting polymers,photochromics,organic superconductors,electrochromics,and many more.Since there is a need to reduce the size of the silicon chip,attaining such technology at the molecular level is essential.Although the experimental verification and modeling of molecular devices present a daunting task,vital breakthroughs have been achieved in this field.This article combines an overview of various molecular components,such as molecular transistors,diodes,capacitors,wires,and insulators,with a discussion of the potential applications of different molecules suitable for such components.We emphasize future developments and provide a brief review of different achievements that have been made regarding graphene-based molecular devices.

A Wire-Shaped Supercapacitor in Micrometer Size Based on Fe_3O_4 Nanosheet Arrays on Fe Wire

One-dimensional(1D, wire-and fiber-shaped)supercapacitors have recently attracted interest due to their roll-up, micrometer size and potential applications in portable or wearable electronics. Herein, a 1D wireshaped electrode was developed based on Fe_3O_4 nanosheet arrays connected on the Fe wire, which was prepared via oxidation of Fe wire in 0.1 M KCl solution(pH 3) with O2-rich environment under 70 °C. The obtained Fe_3O_4 nanosheet arrays displayed a high specific capacitance(20.8 m F cm^(-1) at 10 mV s^(-1)) and long cycling lifespan(91.7% retention after 2500 cycles). Theexcellent performance may attribute to the connected nanosheet structure with abundant open spaces and the intimate contact between the Fe_3O_4 and iron substrate. In addition, a wire-shaped asymmetric supercapacitor was fabricated and had excellent capacitive properties with a high energy density(9 l Wh cm^(-2)) at power density of 532.7 l W cm^(-2) and remarkable long-term cycling performance(99% capacitance retention after 2000 cycles).Considering low cost and earth-abundant electrode material, as well as outstanding electrochemical properties, the assembled supercapacitor will possess enormous potential for practical applications in portable electronic device.

Diffusion of nucleotide excision repair protein XPA along DNA by coarse-grained molecular simulations

Protein XPA plays critical roles in nucleotide excision repair pathway.Recent experimental work showed that the functional dynamics of XPA involves the one-dimensional diffusion along DNA to search the damage site.Here,we investigate the involved dynamical process using extensive coarse-grained molecular simulations at various salt concentrations.The results demonstrated strong salt concentration dependence of the diffusion mechanisms.At low salt concentrations,the one-dimensional diffusion with rotational coupling is the dominant mechanism.At high salt concentrations,the diffusion by three-dimensional mechanism becomes more probable.At wide range of salt concentrations,the residues involved in the DNA binding are similar and the one-dimensional diffusion of XPA along DNA displays sub-diffusive feature.This sub-diffusive feature is tentatively attributed to diverse strengths of XPA-DNA interactions.In addition,we showed that both binding to DNA and increasing salt concentration tend to stretch the conformation of the XPA,which increases the exposure extent of the sites for the binding of other repair proteins.

Semiclassical approach to spin dynamics of a ferromagnetic S = 1 chain

Motivated by recent experimental progress on the quasi-one-dimensional quantum magnet Ni Nb2O6, we study the spin dynamics of an S = 1 ferromagnetic Heisenberg chain with single-ion anisotropy by using a semiclassical molecular dynamics approach. This system undergoes a quantum phase transition from a ferromagnetic to a paramagnetic state under a transverse magnetic field, and the magnetic response reflecting this transition is well described by our semiclassical method.We show that at low temperature the transverse component of the dynamical structure factor depicts clearly the magnon dispersion, and the longitudinal component exhibits two continua associated with single-and two-magnon excitations,respectively. These spin excitation spectra show interesting temperature dependence as effects of magnon interactions. Our findings shed light on the experimental detection of spin excitations in a large class of quasi-one-dimensional magnets.

Self-assembly of insulated molecular wires of a water-soluble cationic PPV and anionic dendrons

Insulated molecular wires of poly(phenylenevinylene) (PPV) were prepared by wrapping the conjugated backbones with dendrons through a noncovalent approach. It was found that electrostatic interaction between the quaternary ammonium groups of PPV-1 and the carboxylate moieties in dendrons induced the packing of dendrons along PPV-1 conjugated backbones. Absorption and emission spectroscopic examinations in solution and solid film indicated that the PPV-1 backbones adopted a more planar and isolated conformation in the complexes. Furthermore, interchain interactions in the complexes could be greatly reduced, improving the quantum yield of PPV-1.

电场作用下分子导线的理论研究

利用从头计算法分别在HF/6-31G,HF/6-31G*,HF/6-31G**,HF/6-31+G,HF/6-31++G,HF/6-31+G*,HF/6-31+G**,HF/D95+*,B3LYP/6-31G*和B3LYP/6-31+G*水平上计算了5个单体的聚乙炔分子导线,从几何构型、SCF能量和分子轨道能级三个方面讨论了外电场对分子导线的影响,给出了聚乙炔分子导线性质与外电场变化的定量关系.

电场对分子线电子结构的影响

从第一性原理出发 ,利用密度泛函理论计算了分子 2 氨基 5 硝基 1,4 二乙炔基 4 苯硫醇基苯与金原子团形成的分子线的电子结构 ,从轨道、能级及吸附电子三个方面讨论了电场对分子线电子结构的影响。该工作将有利于未来纳米电子学器件的设计。

分子线电子输运特性的第一性原理研究

从第一性原理出发 ,利用密度泛函理论研究了SH -C8H16-SH分子和金表面的相互作用 ,并利用分子前线轨道理论和微扰理论定量地确定了该相互作用能常数 ,然后 ,利用弹性散射格林函数方法研究了该分子与金表面形成的分子线的伏 安特性 .研究结果表明 ,当含有硫氢官能团的有机分子化学吸附于金表面时 ,硫原子将与金原子形成以共价键为主的混和键 ,此时 ,扩展的分子轨道使分子线的电导呈现出欧姆特性 ,而对于局域的分子轨道 ,电子的输运只能通过隧道效应来实现 .对分子线伏 安特性的计算结果显示 ,在零偏压附近 ,存在一个电流禁区 ,随着偏压的增加 ,分子线的电导呈现出平台特征 .

外电场作用下寡聚苯分子导线的性质

利用Hartree—Fock方法在6-31G^＊水平上对聚苯分子进行了计算研究．分别从几何构型、分子轨道空间分布和分子轨道能级三个方面讨论了外电场对寡聚苯分子导线的影响，给出了分子导线的性质与外电场的关系．进一步，连接硫原子于聚苯分子的两端，并共价结合在金电极上．利用非平衡格林函数方法对其在0—2．0V偏压下电子输运特征进行了深入研究．