Structure Of Atomic Clusters Research Articles

Dual Modulation of Hydroxyl Action on Ruthenium Surface by Single‐Atom Supports for Alkaline H2 Evolution

AbstractRuthenium (Ru)‐based catalysts are known to accelerate the slow kinetics of the alkaline hydrogen evolution reaction (HER). However, enhancing the transfer kinetics of adsorbed hydroxyl (OHad) remains challenging. Herein, a dual‐regulation strategy is presented to alleviate OH blockage on the catalyst surface, using a cluster‐level Ru electrocatalyst supported by single‐atom CoN4 generated in situ on carbon nanotubes (CNTs). Experimental and theoretical studies demonstrate that introducing oxophilic single‐atom CoN4 can mitigate the strong interaction between Ru and OHad by directly competing for OHad on the Ru surface, thereby preventing Ru site poisoning. Meanwhile, single‐atom CoN4 effectively modifies the electronic structure of Ru atomic clusters (ACs), indirectly optimizing the energy barriers for OH desorption at the Ru interface and promoting OHad release. The electronic interaction between Ru ACs and CoN4 also inhibits Ru atom migration, significantly enhancing catalytic stability. The resulting catalyst shows excellent HER activity at 10 mA cm−2 with a low overpotential of 15 mV in alkaline solution and remains stable at 200 mA cm−2 for over 1000 h. An alkaline anion‐exchange membrane water electrolyzer (AEMWE) using this catalyst can exhibit an ultralow potential (1.785 V at 1 A·cm−2) and high stability at 500 mA·cm−2.

PGA: A new particle swarm optimization algorithm based on genetic operators for the global optimization of clusters.

We have developed a global optimization program named PGA based on particle swarm optimization algorithm coupled with genetic operators for the structures of atomic clusters. The effectiveness and efficiency of the PGA program can be demonstrated by efficiently obtaining the tetrahedral Au20 and double-ring tubular B20, and identifying the ground state clusters through the comparison between the simulated and the experimental photoelectron spectra (PESs). Then, the PGA was applied to search for the global minimum structures of (n = 3-30) clusters, new structures have been found for sizes n = 6, 7, 12, 14, and medium-sized 21-30 were first determined. The high consistency between the simulated spectra and the experimental ones once again demonstrates the efficiency of the PGA program. Based on the ground-state structures of these (n = 3-30) clusters, their structural evolution and electronic properties were subsequently explored. The performance on Au20, B20, , and (n = 3-30) clusters indicates the promising potential of the PGA program for exploring the global minima of other clusters. The code is available for free upon request.

Atomic structure of clusters and GP-zones in an Al-Mg-Si alloy

The structures of atomic clusters and GP-zones preceding precipitation in an Al-0.70Mg-0.85Si-0.15Fe-0.25Mn (wt. %) alloy have been investigated by annular dark field scanning transmission electron microscopy imaging and density functional theory calculations. One analysed condition consisted of one-month natural aging, and another was in a pre-baked state after 24 h aging at 90 °C. To quantify the effect of clusters and GP-zones on microstructure development during a subsequent isothermal artificial aging at 185 °C, hardness evolution was measured, and precipitate statistics was performed at the peak hardness corresponding to 5 h aging. Several types of clusters and GP-zones have been observed and based on structure and visual appearance named 'Disordered Frank-Kasper', 'Square', 'Binocular', and 1β", 2β", 3β", 4β". The first four are most common in the natural aged condition and are associated with a well-known influence on the initial hardness evolution. The last three are fractions of the hardening β" phase and refer to the number of structural units they contain. These GP-zones have an increased density in the pre-baked condition, leading to a rapid increase in hardness during artificial aging and to a finer microstructure of high-density small needle precipitates at peak hardness.

Relationship between relaxation embrittlement and atomic cluster structure in amorphous alloys

Relationship between relaxation embrittlement and atomic cluster structure was explored by simulation and experimental methods for two amorphous alloys: Zr60Cu30Al10 and Zr50Cu40Al10 (referred to as Zr60 and Zr50, respectively). Simulation results from large-scale molecular dynamics revealed that the Zr50 alloy exhibited a higher content of icosahedral clusters, which increased more obvious during the quenching process compared to the Zr60 alloy. As icosahedral clusters exhibit brittleness similar to quasicrystalline structures, we predicted that the Zr50 alloy would have a higher glass transition temperature Tg and more pronounced relaxation-induced brittleness than the Zr60 alloy based on this observation. To validate the predictions, experimental results confirmed the occurrence of relaxation brittleness in Zr50 and relaxation non-brittleness in Zr60, consistent with the XRD analysis and electron microscope-based three-dimensional reconstruction in terms of icosahedral clusters. The agreement between the simulation calculations and the experimental data provides a reference for understanding the mechanism of relaxation embrittlement in amorphous alloys.

Formation of the Short‐Range Order in Liquid Al−Ni−Sn Alloys

AbstractShort‐range order (SRO) in the liquid Al−Ni−Sn alloys has been investigated using the X‐ray diffraction method and Reverse Monte Carlo simulations. Obtained results point out a micro‐inhomogeneous structure of Al−Sn−Ni melts with Sn content between 10 and 65 at.% due to the presence of atomic clusters with the structure of liquid Sn and atomic clusters with Ni−Sn coordination. The influence of the atomic size ratio (size factor) and pair atomic interactions (energy factor) on the short‐range order of the investigated ternary melts are discussed. There is a competition between Al and Sn atoms in the formation of the SRO around Ni atoms due to the difference in bond energy in Ni−Al and Ni−Sn pairs. This competition, as well as a bigger radius of Sn atoms, results in the formation of atomic clusters with liquid Sn‐like local atomic structure.

Electron density mapping of boron clusters via convolutional neural networks to augment structure prediction algorithms.

Determination and prediction of atomic cluster structures is an important endeavor in the field of nanoclusters and thereby in materials research. To a large extent the fundamental properties of a nanocluster are mainly governed by its molecular structure. Traditionally, structure elucidation is achieved using quantum mechanics (QM) based calculations that are usually tedious and time consuming for large nanoclusters. Various structural prediction algorithms have been reported in the literature (CALYPSO, USPEX). Although they tend to accelerate the structure exploration, they still require the aid of QM based calculations for structure evaluation. This makes the structure prediction process quite a computationally expensive affair. In this paper, we report on the creation of a convolutional neural network model, which can give relatively accurate energies for the ground state of nanoclusters from the promolecule density on the fly and could thereby be utilized for aiding structure prediction algorithms. We tested our model on dataset consisting of pure boron nanoclusters of varying sizes.

GAMaterial-A genetic-algorithm software for material design and discovery.

Genetic algorithms (GAs) are stochastic global search methods inspired by biological evolution. They have been used extensively in chemistry and materials science coupled with theoretical methods, ranging from force-fields to high-throughput first-principles methods. The methodology allows an accurate and automated structural determination for molecules, atomic clusters, nanoparticles, and solid surfaces, fundamental to understanding chemical processes in catalysis and environmental sciences, for instance. In this work, we propose a new genetic algorithm software, GAMaterial, implemented in Python3.x, that performs global searches to elucidate the structures of atomic clusters, doped clusters or materials and atomic clusters on surfaces. For all these applications, it is possible to accelerate the GA search by using machine learning (ML), the ML@GA method, to build subsequent populations. Results for ML@GA applied for the dopant distributions in atomic clusters are presented. The GAMaterial software was applied for the automatic structural search for the Ti6 O12 cluster, doping Al in Si11 (4Al@Si11 ) and Na10 supported on graphene (Na10 @graphene), where DFTB calculations were used to sample the complex search surfaces with reasonably low computational cost. Finally, the global search by GA of the Mo8 C4 cluster was considered, where DFT calculations were made with the deMon2k code, which is interfaced with GAMaterial.

Electronic Structure, Stability, and Electrical Mobility of Cationic Silver Oxide Atomic Clusters.

Silver oxide cluster cations (AgnOm+) can readily be produced by a number of methods including atmospheric-pressure spark ablation of pure silver electrodes when trace amounts of oxygen are present in the carrier gas. Here we determine the equilibrium geometries of AgnOm+ clusters (n = 1-4; m = 1-5) using accurate coupled cluster with singles and doubles (CCSD) method, while the stabilization energies are calculated with additional perturbative triples correction (CCSD(T)). Although a number of stable states have been identified, our results show that the AgnOm+ clusters with m = 1 are more stable than those with m ≥ 2 due to the absence of the terminally attached O2 molecule, corroborating recent observations by mass spectrometry. Using the computed structures, we calculate the electrical mobilities of the AgnOm+ clusters and label the values on a respective experimentally determined spectrum in an attempt to better interpret the occurrence of the peaks and troughs in the measurements.

Structures, stabilities and infrared spectra of AgnCr clusters (n=2-12) by density functional theory calculation

Nanoclusters have been emerging as potential building blocks for advanced nanostructured materials with desired catalytic, magnetic, and electronic properties. However, determining the structure of doped atomic clusters encounters many difficulties. A powerful approach to assign the ground state geometries of atomic clusters has been the comparison the recorded vibrational infrared spectra with the corresponding computed ones. In this work, we theoretically investigate the vibrational infrared spectra of the ground-state structures of AgnCr (n=2-12) clusters using density functional theory (DFT) calculations. The results of the investigation are useful for in-depth studies on size growth as well as experiments for determining the cluster structures in the future.

Simulation of nucleation and evolution process of nuclei during solidification of Ti<sub>3</sub>Al alloy

The nucleation mechanism of Ti<sub>3</sub>Al alloy is simulated by the molecular dynamics method in this work. The atomic clusters on different spatial scales are identified in the solidification process by the cluster-type index method (CTIM), and the formation process and the growth process of critical nucleus are studied in depth. It is found that the solidification system contains ten thousands of different types of atomic cluster structures, but only 22 types play a key role in the nucleation process. In the nucleation and growth process of nuclei, the ICO-like cluster, the BCC-like cluster, and the defective FCC cluster and the defective HCP cluster respectively reach their saturation points at the characteristic temperature <i>T</i><sub>1</sub> (1110 K), <i>T</i><sub>2</sub> (1085 K) and <i>T</i><sub>3</sub> (1010 K). And the competition processes of these clusters are revealed according to the changes of their number and spatial distribution with temperature. By tracing the nucleation and growth process of the grain with parallel twin, it is found that the critical crystal nucleus is composed of single-phase FCC structures, and the preferent nucleation of metastable bcc structure is not observed. The twinned structure is formed by the layer-by-layer growth along the close-packed plane. It is also found that the CTIM is more accurate than other methods in revealing the microstructural characteristics during the solidification.

Search for Global Minimum Structures of (n = 1-15) Using xTB-Based Basin-Hopping Algorithm.

A new program for searching global minimum structures of atomic clusters using basin-hopping algorithm based on the xTB method was developed here. The program can be performed with a much higher speed than its replacement directly based on DFT methods. Considering the structural varieties and complexities in finding their global minimum structures, phosphorus cluster cations were studied by the program. The global minimum structures of cationic (n = 1–15) clusters are determined through the unbiased structure searching method. In the last step, further DFT optimization was performed for the selected isomers. For (n = 1–4, 7), the found global minimum structures are in consistent with the ones previously reported; while for (n = 5, 6, 8–12), newly found isomers are more energy-favorable than those previously reported. And those for (n = 13–15) are reported here for the first time. Among them, the most stable isomers of (n = 4–6, 9) are characterized by their C3v, Cs, C2v and Cs symmetry, in turn. But those of (n = 7, 8, 10–12), no symmetry has been identified. The most stable isomers of and are characterized by single P-P bonds bridging units inside the clusters. Further analysis shows that the pnicogen bonds play an important role in the stabilization of these clusters. These results show that the new developed program is effective and robust in searching global minimum structures for atom clusters, and it also provides new insights into the role of pnicogen bonds in phosphorus clusters.

Activation of pyramidal II slips at room temperature in Mg–Zn–Y 18R and 14H long-period stacking ordered phases

The 18R and 14H long-period stacking ordered (LPSO) phases were generally considered that only the basal and non-basal <a> slips and kink banding could be activated during quasi-state deformation at room temperature. Here, we confirm that the pyramidal II <c+a> slips can also be activated in the 18R LPSO phase by quasi-state nanoindentation and in the 14H LPSO phase by cold roll with a rolling direction parallel to the (0001) plane. Due to the interaction between the Zn6Y8 atomic clusters in the LPSO phases and the pyramidal II <c+a> dislocations, the pyramidal II <c+a> slips are localized in the well-defined slip bands while the chemically ordered structure of Zn6Y8 atomic clusters is disrupted to be disordered. Additionally, the interaction also induces Zn/Y atoms segregation at the two edges of the slip band. Our results unravel the origin for the excellent room temperature plasticity in the LPSO phases.

Preface: 3rd International Conference on Green Energy and Sustainable Development (GESD 2020)

This proceeding includes original and peer-reviewed research papers from the 3rd International Conference on Green Energy and Sustainable Development (GESD 2020), which held on November 14-15, 2020. GESD 2020 is organized by Research Center of Engineering and Science, co-organized by Chongqing University, Northeast Petroleum University, Huazhong University of Science and Technology, Asian Union of Information Technology, sponsored by Wanxiang Group Technology Center, CCCC Second Harbour Engineering Company Ltd., Chishun Chemical.This GESD was held ONLINE via Tencent meeting/VooV Meeting. During the COVID-19 outbreak, many academic exchange activities were affected, such as visas, venues with more than 30 people, possible 14-day quarantine across regions, epidemic prevention measures, etc. After comprehensive consideration, the conference organizing committee decided to hold GESD 2020 online.The aim of GESD 2020 was to provide a platform for researchers, engineers, academicians, as well as industrial professionals, to present their research results and development activities in Green Energy and Sustainable Development. It provides opportunities for the delegates to exchange new ideas and application experiences, to establish business or research relations and to find global partners for future collaboration. This two-day conference was being organized in invited keynote talks and three Parallel Sessions: SESSION I: Green Energy & Sustainable Energy and Power; SESSION II: Resource Extraction, Utilization & Sustainable Development; SESSION III: Environmental Sustainability and Green Technologies.The keynote speakers and their speech topics are as follows.Prof. Zhou from China University of Petroleum, and his speech topics: Proposed the concept of chemical sequence stratigraphy and established the sea The theory and method of quantitative calculation of sea level change and intermittent missing time of facies stratum; found a group of Si-O atomic cluster structures represented by Si3O4, and systematically discussed the possible cluster molecular structure, and established the original solar nebula A stationary model for the statistical thermodynamics of the atomic clusters in the middle.Prof. Wang from Xi’an Jiaotong University, and his speech topics: Key technology and system integration for high-concentration refractory organic wastewater/sludge supercritical water treatment and energy utilization, advanced combustion technology (supercritical hydrothermal combustion, chemical chain combustion), waste/biomass pyrolysis gasification and fly ash Melting technology, high-temperature metallurgical slag dry centrifugal granulation and waste heat efficient recovery technology and system integration, high-efficiency environmental protection boiler technology (garbage and biomass pyrolysis gasifier, oil production wastewater directly heated steam injection boiler, SAGD steam drum furnace, waste Liquid incinerators, vertical industrial pulverized coal kilns, supercritical hydrothermal combustion multiple thermal fluid generators, etc.) development, geothermal energy/(microalgae) biomass energy development, multi-energy complementary green low-carbon intelligent energy system integration and Optimization research.Prof. Liu from Huazhong University of Science and Technology, and his speech topics: Energy recovery of automobile shock absorbers, energy conversion efficiency and vehicle energy management, also engaged in the modeling and simulation of complex systems in multidisciplinary fields, hydraulic and fluid mechanics simulation, system dynamics simulation, energy conversion and efficiency simulation and verification.All full paper submissions to this GESD would be sent to at least two reviewers and evaluated based on originality, technical or research content, correctness, relevance to conference, contributions, and readability. The full paper submissions were chosen based on technical merit, interest, applicability, and how well they fit a coherent and balanced technical program. GESD 2020 received 412 manuscripts. And 279 submissions had been accepted by our reviewers. The Committees of GESD 2020 invested great efforts in reviewing the papers submitted to the conference and organizing the sessions to enable the participants to gain maximum benefit.Lin LiuJianguo MingZhipeng MaConference Organizing Committee

Probing the Microstructure in Pure Al & Cu Melts: Theory Meets Experiment.

In the present work, a new model of the atomic cluster structure, which is determined by metal Wulff construction with the crystal structure inside, is proposed to describe the structures of metallic melts. The shapes of the structures are determined by surface energies of different crystal plane groups, calculated from density functional theory (DFT), while the size is given by the pair distribution function (PDF) of the experimental high-temperature X-ray diffraction (HTXRD). Taking Aluminum (Al) and Copper (Cu) as the representative examples, we demonstrate that the simulated XRD curves from present models match the experimental results quite well, not only regarding the position and width of the peaks but also the relative intensity of the first and second peaks. These results indicate a successful model to describe the properties of metallic melts. The model also explains a main peak deviation phenomenon between the XRD of metallic melt and the solid ones in pure metal Al. Finally, a physical picture of metallic melt is given, which is mainly composed of atomic cluster structures and free atoms around them.

Electronic Structure of Nanoclusters by Quantum Monte Carlo Methods

The valence electron binding energies of the atomic clusters $$\hbox {XAl}_3^-$$ (X = Si, Ge, and Sn) and $$\hbox {YAl}_4^-$$ (Y = Li, Na, and Cu) are investigated using a combination of the fixed-node diffusion quantum Monte Carlo method (FN-DMC), the density functional theory, and the Hartree–Fock approximation. A brief review of the used theoretical approaches is presented with emphasis on the variational and diffusion Monte Carlo techniques and their applications to study the electronic structures of atomic clusters. The obtained results for the vertical detachment energies (VDE) from the FN-DMC are in excellent agreement with available experimental photoelectron spectroscopy data. A comparison between the FN-DMC results and HF ones allows to quantify the electron correlation effects and their impact on the stability of the clusters. The analysis reveals that the electron correlation enhances the VDE of the atomic clusters significantly and plays an essential role in their stability.

Small atomic clusters: quantum chemical research of isomeric composition and physical properties

In this review, we give a brief summary of methodological and computational aspects of determination of structure and different size-dependent properties of small atomic clusters by means of computational quantum chemistry. Particular attention is paid to the accurate calculation of thermodynamic properties of clusters with allowance for the vibrational anharmonicity and contribution of excited electronic states. We describe in detail the problems and consequences related to accounting for the contribution of isomeric forms to the observable physical and thermodynamic characteristics. The physical size-dependent properties discussed in this review are the binding energy, zero-point energy, collision diameter, polarizabilities, ionization potential, electron affinity, specific heat capacity, and reduced Gibbs energy. The major part of the review deals with the methodology for physically sound extrapolating the multitude of size-dependent physical and thermodynamic properties of small clusters toward significantly larger (nanometer- and micrometer-sized) particles.

Quantitative and qualitative correlations by atomistic determination for the precipitated phases in Al–Li–Cu system

The atomic cluster structures, stability and properties of the precipitated phases in Al–Li–Cu system, together with the corresponding quantitative and qualitative correlations are investigated by performing atomistic simulations. It is found that the characteristic principal clusters could accurately reflect the local atomic configuration and the short-range-order structural feature of the Al–Li–Cu alloys. These principal atomic clusters are with coordination number (CN) ranging from 10 to 14, and most are with CN12. The mass density of the Al–Li–Cu precipitated phases changes linearly as the solute-concentration. The stability of Al–Li precipitated phases decreases as the solute content, and the cohesive energy of the Al–Cu precipitated phases is higher than that of the Al–Li precipitated phases. Besides, Al4Cu9, AlCu2, AlCu, Al3Li and Al3Li2 phases have larger elastic moduli and higher hardness than the other precipitated phases. The Al–Cu precipitated phases exhibit better plasticity than the Al–Li precipitated phases. All of these Al–Li–Cu precipitated phases are thermodynamically and mechanically stable. Analysis on the band structures and the density of states indicates that these Al–Li–Cu precipitated phases behave the conductive property. There is a negative correlation between the nucleation barrier and the driving force during the precipitation at different aging temperatures, as exemplified by the θ′-Al2Cu precipitate.

Atomic structure of an amorphous Ti–Ta-based surface alloy synthesized on a TiNi substrate by an electron-beam method

Abstract The research presents the atomic (cluster) structure of an amorphous Ti–Ta-based surface alloy fabricated on a TiNi substrate by electron beam method. Transmission electron microscopy and “cluster-plus-glue-atom” model were utilized to resolve the atomic-level structure of amorphous phase by means of real-space radial distribution functions. It has been found that ~ 2 μm amorphous surface layer has gradient chemical composition and, relative to conventional metallic glasses, appears nonhomogeneous in structure depending on various atomic arrangements in the first and second neighboring shells. The amorphous Ti–Ta-based surface alloy is shown to have structure with the atomic medium-range order and can be described by principal cluster [Ti–Ti10Ni4]Ni2Ta of Ti2Ni intermetallic compound with icosahedral orientational ordering.

Growth-Rule-Guided Structural Exploration of Thiolate-Protected Gold Nanoclusters.

Understanding the structure and structure-property relationship of atomic and ligated clusters is one of the central research tasks in the field of cluster research. In chemistry, empirical rules such as the polyhedral skeleton electron pair theory (PSEPT) approach had been outlined to account for skeleton structures of many main-group atomic and ligand-protected transition metal clusters. Nonetheless, because of the diversity of cluster structures and compositions, no uniform structural and electronic rule is available for various cluster compounds. Exploring new cluster structures and their evolution is a hot topic in the field of cluster research for both experiment and theory. In this Account, we introduce our recent progress in the theoretical exploration of structures and evolution patterns of a class of atomically precise thiolate-protected gold nanoclusters using density functional theory computations. Unlike the conventional ligand-protected transition metal compounds, the thiolate-protected gold clusters demonstrate novel metal core/ligand shell interfacial structures in which the Au m(SR) n clusters can be divided into an ordered Au(0) core and a group of oligomeric SR[Au(SR)] x ( x = 0, 1, 2, 3, ...) protection motifs. Guided by this "inherent structure rule", we have devised theoretical methods to rapidly explore cluster structures that do not necessarily require laborious global potential energy surface searches. The structural predictions of Au38(SR)24, Au24(SR)20, and Au44(SR)28 nanoclusters were completely or partially verified by the later X-ray crystallography studies. On the basis of the analysis of cluster structures determined by X-ray crystallography and theoretical prediction, a structural evolution diagram for the face-centered-cubic (fcc)-type Au m(SR) n clusters with m up to 92 has been preliminarily established. The structural evolution diagram indicates some basic structural and electronic evolution patterns of thiolate-protected gold nanoclusters. The fcc Au m(SR) n clusters show a genetic structural evolution pattern in which each step of cluster size increase results in the formation of another Au4 tetrahedron or Au3 triangle unit in the Au core, and every increase of a structural unit in the Au core leads to an increase of two electrons in the whole cluster. The unique one- or two-dimensional cluster size evolution, the isomerism of the Au-S framework, and the formation of a double-helical and cyclic tetrahedron network in the fcc Au m(SR) n clusters all can be addressed from this evolution pattern. The summarized cluster structural evolution diagrams enable us to further explore more stable cluster structures and understand their structure-electronic structure-property relationships.

AUTOMATON: A Program That Combines a Probabilistic Cellular Automata and a Genetic Algorithm for Global Minimum Search of Clusters and Molecules.

A novel program for the search of global minimum structures of atomic clusters and molecules in the gas phase, AUTOMATON, is introduced in this work. This program involves the following: first, the generation of an initial population, using a simplified probabilistic cellular automaton method, which allows easy control of the adequate distribution of atoms in space; second, the fittest individuals are selected to evolve, through genetic operations (mating and mutations), until the best candidate for a global minimum surfaces. In addition, we propose a simple way to build the descendant structures by establishing a ranking of genes to be inherited. Thus, by means of a chemical formula checker procedure, genes are transferred to the offspring, ensuring that they always have the appropriate type and number of atoms. It is worth noting that a fraction of the fittest group is subject to mutation operations. This program also includes algorithms to identify duplicate structures: one based on geometric similarity and another on the similar distribution of atomic charges. The effectiveness of the program was evaluated in a group of 45 molecules, considering organic and organometallic compounds (benzene, cyclopentadienyl anion, and ferrocene), Zintl ion clusters [Sn9- m- nGe mBi n](4- n)- ( n = 1-4 and m = 0-(9- n)), star-shaped clusters (Li7E5+, E = BH, C, Si, Ge) and a variety of boron-based clusters. The global minimum and the lowest-energy isomers reported in the literature were found for all the cases considered in this article. These results successfully prove AUTOMATON's effectiveness on the identification of energetically preferred structures of a wide variety of chemical species.