Structural and energetic analysis of copper clusters: MD study of Cu n (n = 2-45)

Abstract

Simulações usando a dinâmica molecular foram efetuadas, considerando-se um potencial empírico para investigar geometrias, padrões de crescimentos, estabilidades de estruturas e energias para clusters de Cu n (n = 2-45). Os clusters estáveis otimizados foram calculados pelo rearranjo via processo de colisão. O presente procedimento apresenta-se como uma alternativa eficiente para a identificação do crescimento de clusters e como uma técnica de otimização. Foi verificado que os clusters de cobre preferem formar estruturas compactas tridimensionais em determinadas configurações enquanto os sistemas de tamanho médio apresentam simetria esférica. Além disso, também foram observadas correlações entre os arranjos atômicos e os números mágicos dos clusters. Particularmente, verificou-se que Cu 26 tem uma estabilidade equivalente ao sistema Cu 13 . Molecular dynamics simulations, via an empirical potential, have been performed in order to investigate geometries, growing patterns, structural stabilities, energetics, and magic sizes of copper clusters, Cu n (n = 2-45). Possible optimal stable structures of the clusters have been generated through following rearrangement collision of the system in fusion regime. This process serves as an efficient alternative to the growing path identification and the optimization techniques. It has been found that copper clusters prefer to form three-dimensional compact structures in the determined configurations and the appearances of medium sizes are five fold symmetry on the spherical clusters. Moreover, relevant relations between atomic arrangements in the clusters and the magic sizes have been observed. Cu 26 may be accepted as another putative magic size like Cu 13 .Keywords: copper, cluster, potential energy function, molecular dynamics IntroductionClusters are quite different from solid-state materials. They are aggregates of nanoscale size, with an intermediate state of matter between molecules and bulk. They also exhibit a range of unusual physical and chemical properties, such as structural, electronic, and thermodynamic. Metallic clusters have been the subjects of intense research. Due to their broad applications toward biology, catalysis, and nanotechnology, research on clusters has shown considerable development in both experimental and theoretical investigations. [1][2][3][4][5][6] Understanding the intricate connection between the atomic and electronic structures can represent an important preliminary step toward the possible use of metal nanoclusters in future nanotechnological applications. [1][2][3][4][5][6] In this respect, the changes of cluster properties as a function of size, such as evolution from small to large clusters, is one of the most interesting issues. 6 Systematic structural studies represent the starting point for understanding other general cluster properties. Hence, enormous efforts are devoted to determine the lowest energy structures of transition metal (TM) clusters. 5-10Unfortunately, determination of equilibrium structures, and of atomic arrangemen...

Structural Optimization of (Aum‐Agn‐Pdo‐Ptp) (m=10 and n+o+p=10) Tetrametallic Clusters Using a Combined Empirical Potential‐Density Functional (EP‐DF) Approach

“…The parameters used for the Gupta potential are given in Table . The Au 20 (theo) possess a tetrahedral pyramidal structure with T d symmetry,, similar to the Cu 20 (theo) structure . The strong triply degenerated t 2 vibration for Au 20 (exp) clusters is observed at 148 cm −1 whereas the vibration for Au 20 (theo) clusters occur at 155 cm −1 .The ω f (lowest and highest) values for these clusters are (24, 154) cm −1 which agrees well to the previous results .…”

DFT Study of Small Palladium Clusters Pdn and Their Interaction with a CO Ligand (n = 1–9)

“…It can be explained by the fact that the sphere of coordination of palladium atoms tends to a limit as the cluster nuclearity increases. Optimizations with molecular dynamics were carried out for sizes up to 40 atoms [13] and show that the limit of the cohesive energy is far from being achieved with a nuclearity of 9. The stability of a cluster with a given nuclearity n can also be compared to its closest neighbours (Pd n-1 and Pd n+1 ) through fragmentation reactions.…”

“…[8][9][10][11][12] Recently, palladium clusters with larger nuclearity were also studied by molecular dynamics. [13] Interactions of ligands with the metal core have also been the subject of a series of works which include, among others, interactions with CO, [14,15] NO, [16] S and Cl, [17] O 2 [18] or H and CH x . [19] In this work, we intend to push further the investigation of these species by addressing in greater detail their electronic structure.…”

σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity

“…In broad terms, the most favorable atomic conformation, magnetic spin-state and electronic valence configuration vary largely for clusters of different TM elements. A common feature is that as the size of the cluster grows, the favorable structure converges towards the compact, close-packed, bulk structure of the corresponding metal [53][54][55][56]. However, at the (sub) nanometer scale, it has been established that clusters of e.g., Rh, Ru, and Ir, adopt an open cubic structure, whereas 3d clusters of Cu, Au and Pd are often found to be compact and possibly disordered [14,57].…”