Global optimization of bimetallic cluster structures. I. Size-mismatched Ag–Cu, Ag–Ni, and Au–Cu systems

Rapallo, Arnaldo; Rossi, Giulia; Ferrando, Riccardo; Fortunelli, Alessandro; Curley, B. C.; Lloyd, Lesley D.; Tarbuck, Gary; Johnston, Roy L.

doi:10.1063/1.1898223

Cited by 317 publications

(308 citation statements)

References 55 publications

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“…Besides being poorly miscible in bulk phases 42 , these systems have the element of larger atomic radius (Ag or Au) presenting smaller cohesive and surface energies than the other element. These features are all in favour of Ag or Au surface segregation in these nanoparticles, a behaviour that has been confirmed, both experimentally and computationally, by several studies 2,[5][6][7][9][10][11][13][14][15][16][17][19][20][21][22][23][24][25][29][30][31][32]35 . However, the fact that the cluster surface is expected to contain mostly Ag or Au does not determine completely chemical ordering.…”

Section: Introductionmentioning

confidence: 75%

Morphological instability of core-shell metallic nanoparticles

Bochicchio¹,

Ferrando²

2013

Phys. Rev. B

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213

209

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Bimetallic nanoparticles (often known as nanoalloys) with core-shell arrangement are of special interest in several applications, such as in optics, catalysis, magnetism and biomedicine. Despite wide interest in applications, the physical factors stabilizing the structures of these nanoparticles are still unclear to a great extent, especially for what concerns the relationship between geometric structure and chemical ordering pattern. Here global-optimization searches are performed in order to single out the most stable chemical ordering patterns corresponding to the most important geometric structures, for a series of weakly miscible systems, including AgCu, AgNi, AgCo and AuCo. The calculations show that (i) the overall geometric structure of the nanoalloy and the shape and placement of its inner core are strictly correlated; (ii) centered cores can be obtained in icosahedral nanoparticles but not in crystalline or decahedral ones, in which asymmetric quasi-Janus morphologies form; (iii) in icosahedral nanoparticles, when the core exceeds a critical size, a new type of morphological instability develops, making the core asymmetric and extending it towards the nanoparticle surface; (iv) multi-center patterns can be obtained in polyicosahedral nanoalloys.Analogies and differences between the instability of the core in icosahedral nanoalloys and the StranskiKrastanov instability occurring in thin-film growth are discussed. All these issues are crucial for designing strategies to achieve effective coatings of the cores.a Corresponding author,

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Section: Introductionmentioning

confidence: 75%

Morphological instability of core-shell metallic nanoparticles

Bochicchio¹,

Ferrando²

2013

Phys. Rev. B

Self Cite

213

209

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“…Low energy structures of similarly sized metallic (e.g. Au 20 41 ) and bimetallic 42 clusters have been obtained using genetic algorithms combined with DFT to evaluate energies and carry out geometry optimizations [41][42][43] .…”

Section: Introductionmentioning

confidence: 99%

Discovering Amorphous Indium Phosphide Nanostructures with High-Temperature ab Initio Molecular Dynamics

2015

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We employ high-temperature ab initio molecular dynamics (AIMD) as a sampling approach to discover low-energy, semiconducting, indium phosphide nanostructures. Starting from under-coordinated models of InP (e.g. a single layer of InP (111)), rapid rearrangement into a stabilized, higher-coordinate but amorphous cluster is observed across the size range considered (In 3 P 3 to In 22 P 22 ). These clusters exhibit exponential decrease in energy per atom with system size as effective coordination increases, which we define through distance-cutoff coordination number assignment and partial charge analysis. The sampling approach is robust to initial configuration choice as consistent results are obtained when alternative crystal models or computationally efficient generation of structures from sequential addition and removal of atoms are employed. This consistency is observed across the 66 structures compared here, and even when as many as five approaches are compared, the average difference in energy per pair of atoms in these structures is only 1.5 kcal/mol at a given system size. Interestingly, the energies of these amorphous clusters are lower than geometry optimized spherical models of bulk InP typically used for simulations of quantum dots. Favorable energetics appear correlated to highlycoordinated indium and phosphorus with coordination numbers up to five and seven, respectively, as well as formation of phosphorus-phosphorus bonds.2

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“…[1] The existing experimental as well as theoretical works on the M-NM binary nano-clusters in general, bring out an interesting common feature which suggests that when the components of the binary nano clusters have a miscibility gap in their bulk phases, a core-shell like chemical ordering is more likely to form in order to minimize the internal strain. [19,[36][37][38] The situation for the Ni-Ag nanoclusters is unfortunately confusing both from the point of view of experimental as well as theoretical studies, with some reports supporting core-shell like configuration following the general trend of M-NM binary clusters, [39][40][41][42] while others report formation of homogeneous alloy structure. [43][44][45][46][47]For example, global optimization of the NiAg nano clusters using some semi-empirical potentials with the tight-binding second moment approximation indicated poly-icosahedral structure of core-shell type for cluster sizes of 34 and 38 atoms.…”

Section: Introductionmentioning

confidence: 99%

First principles study of bimetallic Ni13−nAgn nano-clusters (n = 0–13): Structural, mixing, electronic, and magnetic properties

Datta

Raychaudhuri

Saha‐Dasgupta

2017

The Journal of Chemical Physics

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Using spin polarized density functional theory (DFT) based calculations, combined with ab-initio molecular dynamics simulation, we carry out a systematic investigation of the bimetallic Ni13−nAgn nano clusters, for all compositions. This includes prediction of the geometry, mixing behavior, and electronic properties. Our study reveals a tendency towards formation of a core-shell like structures, following the rule of putting Ni in high coordination site and Ag in low coordination site. Our calculations predict negative mixing energies for the entire composition range, indicating mixing to be favored for the bimetallic small sized Ni-Ag clusters, irrespective of the compositions. The magic composition with the highest stability is found for the NiAg12 alloy cluster. We investigate the microscopic origin of core-shell like structure with negative mixing energy, in which the Ni-Ag inter-facial interaction is found to play role. We also study the magnetic properties of the Ni-Ag alloy clusters. The Ni dominated magnetism, consists of parallel alignment of Ni moments while the tiny moments on Ag align in anti-parallel to Ni moments. The hybridization with Ag environment causes reduction of Ni moment.

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Global optimization of bimetallic cluster structures. I. Size-mismatched Ag–Cu, Ag–Ni, and Au–Cu systems

Cited by 317 publications

References 55 publications

Morphological instability of core-shell metallic nanoparticles

Morphological instability of core-shell metallic nanoparticles

Discovering Amorphous Indium Phosphide Nanostructures with High-Temperature ab Initio Molecular Dynamics

First principles study of bimetallic Ni13−nAgn nano-clusters (n = 0–13): Structural, mixing, electronic, and magnetic properties

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