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Kaappa S, Larsen C, Jacobsen KW. Atomic Structure Optimization with Machine-Learning Enabled Interpolation between Chemical Elements. PHYSICAL REVIEW LETTERS 2021; 127:166001. [PMID: 34723620 DOI: 10.1103/physrevlett.127.166001] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
We introduce a computational method for global optimization of structure and ordering in atomic systems. The method relies on interpolation between chemical elements, which is incorporated in a machine-learning structural fingerprint. The method is based on Bayesian optimization with Gaussian processes and is applied to the global optimization of Au-Cu bulk systems, Cu-Ni surfaces with CO adsorption, and Cu-Ni clusters. The method consistently identifies low-energy structures, which are likely to be the global minima of the energy. For the investigated systems with 23-66 atoms, the number of required energy and force calculations is in the range 3-75.
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Affiliation(s)
- Sami Kaappa
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Casper Larsen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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2
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Orlando Morais F, Andriani KF, Da Silva JLF. Investigation of the Stability Mechanisms of Eight-Atom Binary Metal Clusters Using DFT Calculations and k-means Clustering Algorithm. J Chem Inf Model 2021; 61:3411-3420. [PMID: 34161078 DOI: 10.1021/acs.jcim.1c00253] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we report density functional theory calculations combined with the k-means clustering algorithm and the Spearman rank correlation analysis to investigate the stability mechanisms of eight-atom binary metal AB clusters, where A and B are Fe, Co, Ni, Cu, Ga, Al, and Zn (7 unary and 21 binary clusters). Based on the excess energy analysis, the six most stable binary clusters are NiAl, NiGa, CoAl, FeNi, NiZn, and FeAl, and except for FeNi, their highest energetic stabilities can be explained by the hybridization of the d- and sp-states, which is maximized at the 50% composition, i.e., A4B4. Based on the Spearman correlation analysis, the energetic stability of the binary clusters increases with an increase in the highest occupied molecule orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy separation, which can be considered as a global descriptor. Furthermore, reducing the total magnetic moment values increases the stability for binary clusters without the Fe, Co, and Ni species, while the binary FeB, CoB, and NiB clusters increase their energetic stability with a decrease in the cluster radius, respectively, i.e., an energetic preference for compact structures.
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Affiliation(s)
- Felipe Orlando Morais
- São Carlos Institute of Physics, University of São Paulo, P.O. Box 400, 13566-590 São Carlos, SP, Brazil
| | - Karla F Andriani
- São Carlos Institute of Chemistry, University of São Paulo, P.O. Box 780, 13560-970 São Carlos, SP, Brazil
| | - Juarez L F Da Silva
- São Carlos Institute of Chemistry, University of São Paulo, P.O. Box 780, 13560-970 São Carlos, SP, Brazil
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3
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Salcedo A, Irigoyen B. DFT insights into structural effects of Ni-Cu/CeO 2 catalysts for CO selective reaction towards water-gas shift. Phys Chem Chem Phys 2021; 23:3826-3836. [PMID: 33533765 DOI: 10.1039/d0cp05613h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The water-gas shift (WGS) reaction is a key step in hydrogen production, particularly to meet the high-purity H2 requirement of PEM fuel cells. The catalysts currently employed in large-scale WGS plants require a two-step process to overcome thermodynamic and kinetic limitations. Ni-Cu/CeO2 solids are promising catalysts for the one-step process required for small-scale applications, as the addition of Cu hinders undesired methanation reactions occurring on Ni/CeO2. In this work, we performed calculations on Ni4-xCux/CeO2(111) systems to evaluate the influence of cluster conformation on the selectivity towards water-gas shift. The structure and miscibility of CeO2-supported Ni4-xCux clusters were investigated and compared with those of gas-phase clusters to understand the effect of metal-support interactions. The adsorption of CO onto apical Ni and Cu atoms of Ni4-xCux/CeO2(111) systems was studied, and changes in the C-O bond strength were confirmed at the electronic level by investigating shifts in the 3σ and 1π orbitals. The selectivity towards WGS was evaluated using Brønsted-Evans-Polanyi relations for the C-O activation energy. Overall, a strengthening of the C-O bond and an increase in CO dissociation energy were verified on Cu-containing clusters, explaining the improvement in selectivity of Ni4-xCux/CeO2(111) systems.
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Affiliation(s)
- Agustín Salcedo
- Universidad de Buenos Aires, Facultad de Ingeniería, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina. and CONICET - Universidad de Buenos Aires, Instituto de Tecnologías del Hidrógeno y Energías Sostenibles (ITHES), Pabellón de Industrias, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina
| | - Beatriz Irigoyen
- Universidad de Buenos Aires, Facultad de Ingeniería, Departamento de Ingeniería Química, Pabellón de Industrias, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina. and CONICET - Universidad de Buenos Aires, Instituto de Tecnologías del Hidrógeno y Energías Sostenibles (ITHES), Pabellón de Industrias, Ciudad Universitaria, C1428EGA Buenos Aires, Argentina
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4
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DFT Study of the Interaction of Trialkylamines with
$$\hbox {Ni}_{4}$$
Ni
4
-Clusters. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2019. [DOI: 10.1007/s13369-018-3420-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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Arslan H, Garip AK, Johnston RL. Theoretical study of the structures and chemical ordering of cobalt–palladium nanoclusters. Phys Chem Chem Phys 2015; 17:28311-21. [DOI: 10.1039/c5cp01029b] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Global optimization of 1 : 1 compositions of (Co–Pd)N/2 up to N = 150 and all compositions of 34- and 38-atom binary clusters has been performed using a genetic algorithm, coupled with the Gupta empirical potential to model interatomic interactions.
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Affiliation(s)
- Haydar Arslan
- Bülent Ecevit University
- Department of Physics
- 67100 Zonguldak
- Turkey
| | - Ali Kemal Garip
- Bülent Ecevit University
- Department of Physics
- 67100 Zonguldak
- Turkey
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6
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Pakiari AH, Pahlavan F. The electronic structures of small Ni(n) (n=2-4) clusters and their interactions with ethylene and triplet oxygen: a theoretical study. Chemphyschem 2014; 15:4055-66. [PMID: 25263214 DOI: 10.1002/cphc.201402467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Indexed: 11/10/2022]
Abstract
Density functional theory (DFT) calculations of small nickel clusters and their interacting systems are carried out using the BLYP and B97-2 methods, after DFT calibration. All bare nickel clusters in this study have high multiplicities and are paramagnetic. Our results for the interactions between ethylene and oxygen with Ni(n) (n=2-4) clusters at different adsorption modes show that for ethylene, π-orientation is preferred, and that oxygen adsorption in a bridge mode is stronger than on-top coordination. Vibrational frequency analysis reveals that the vibrational modes of ethylene π-coordinated to nickel clusters converge toward the corresponding value for surface-bound ethylene, as the cluster size increases from two to four, showing that finite clusters can be used as localized models for ligand adsorption on nickel surfaces. We also calculate DFT global reactivity descriptors, chemical potential and hardness, and use these to predict the relative stability and reactivity of each bare cluster.
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Affiliation(s)
- Ali H Pakiari
- Chemistry Department, College of Science, Shiraz University, Eram square, Eram street 7146713565 Shiraz (Iran).
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7
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Sushko GB, Verkhovtsev AV, Solov'yov AV. Validation of classical force fields for the description of thermo-mechanical properties of transition metal materials. J Phys Chem A 2014; 118:8426-36. [PMID: 24766551 DOI: 10.1021/jp501723w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
It is demonstrated that classical force fields validated through the density functional theory (DFT) calculations of small titanium and nickel clusters can be applied for the description of thermo-mechanical properties of corresponding materials. This has been achieved by means of full-atom molecular dynamics simulations of nanoindentation of amorphous and nanostructured Ti and Ni-Ti materials. The theoretical analysis performed and comparison with experimental data demonstrate that the utilized classical force fields for Ti-Ti, Ni-Ni and Ni-Ti interactions describe reasonably well hardness and the Young's modulus of these materials. This observation is of the general nature and can be utilized for similar numerical exploration of thermo-mechanical properties of a broad range of materials.
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Affiliation(s)
- Gennady B Sushko
- Frankfurt Institute for Advanced Studies, Goethe-Universität Frankfurt am Main , Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany
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9
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Bernardi A, Ciabatti I, Femoni C, Iapalucci MC, Longoni G, Zacchini S. Ni-Cu tetracarbide carbonyls with vacant Ni(CO) fragments as borderline compounds between molecular and quasi-molecular clusters. Dalton Trans 2012; 42:407-21. [PMID: 23069730 DOI: 10.1039/c2dt31719b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of [Ni(9)C(CO)(17)](2-) with [Cu(CH(3)CN)(4)][BF(4)] (1.1-1.5 equiv.) afforded the first Ni-Cu carbide carbonyl cluster, i.e., [H(2)Ni(30)C(4)(CO)(34){Cu(CH(3)CN)}(2)](4-) ([H(2)1](4-)). This has been crystallised in a pure form with miscellaneous [NR(4)](+) (R = Me, Et) cations, as well as co-crystallised with [H(2)Ni(29)C(4)(CO)(33){Cu(CH(3)CN)}(2)](4-) ([H(2)2](4-)) which differs from [H(2)1](4-) by a missing Ni(CO) fragment. By increasing the [Cu(CH(3)CN)(4)](+)/[Ni(9)C(CO)(17)](2-) ratio to 1.7-1.8, the closely related [H(2)Ni(30)C(4)(CO)(35){Cu(CH(3)CN)}(2)](2-) ([H(2)3](2-)), [H(2)Ni(29)C(4)(CO)(34){Cu(CH(3)CN)}(2)](2-) ([H(2)4](2-)), and [H(2)Ni(29)C(4)(CO)(32)(CH(3)CN)(2){Cu(CH(3)CN)}(2)](2-) ([H(2)5](2-)) dianions have been obtained. Replacement of Cu-bonded CH(3)CN with p-NCC(6)H(4)CN afforded, after protonation of the tetra-anion, mixtures of [H(3)Ni(30)C(4)(CO)(34){Cu(NCC(6)H(4)CN)}(2)](3-) ([H(3)6](3-)) and [H(3)Ni(29)C(4)(CO)(33){Cu(NCC(6)H(4)CN)}(2)](3-) ([H(3)7](3-)). The species 1-7 display a common Ni(28)C(4)Cu(2) core and differ for the charge, the presence of additional Ni atoms, the number and nature of the ligands, even though they are obtained under similar experimental conditions and often in mixtures. Their nature in solution has been investigated via FT-IR, chemical and electrochemical methods. Electrochemical studies, besides confirming the poly-hydride nature of these clusters, show that they undergo different redox processes with features of chemical reversibility, and this might be taken as proof of the incipient metallisation of their metal cores.
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Affiliation(s)
- Alessandro Bernardi
- Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4-40136 Bologna, Italy
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10
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Yamauchi T, Tsukahara Y, Sakata T, Mori H, Yanagida T, Kawai T, Wada Y. Magnetic Cu-Ni (core-shell) nanoparticles in a one-pot reaction under microwave irradiation. NANOSCALE 2010; 2:515-523. [PMID: 20644753 DOI: 10.1039/b9nr00302a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We successfully prepared face-centered cubic (fcc) Cu-Ni (core-shell) nanoparticles by intramolecular reduction of formate complexes of Cu(2+) and Ni(2+) with long-chain amine ligands in a one-pot reaction within an extremely short time realized only under microwave irradiation. Observation by an HAADF-STEM technique showed that the nanostructure in one particle consisted of a Ni-rich shell and a Cu-rich core. Cu(4)Ni(6) nanoparticles with an average size of 11.7 nm were comprised of a Cu core with a diameter of ca. 6.0 nm, a Ni shell ca. 1.6 nm thick and a 0.9 nm thick interlayer of mixed Cu-Ni alloy between the Cu core and the Ni shell. Both the oxidation characteristics and the magnetic properties were dramatically affected by the molar ratios of Cu : Ni in the Cu-Ni nanoparticles. The magnetization of Cu(3)Ni(7) and Cu(4)Ni(6) comprised of a diamagnetic Cu-rich core, ferromagnetic Ni-rich shell and antiferromagnetic NiO-rich layer on the particle surface showed an exchange bias (209 and 143 Oe, respectively).
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Affiliation(s)
- Tomohisa Yamauchi
- Graduate School of Engineering, Osaka University, 2-1 Yamada-oka Suita, Osaka 565-0871, Japan
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Venkataramanan NS, Sahara R, Mizuseki H, Kawazoe Y. Titanium-Doped Nickel Clusters TiNin (n = 1−12): Geometry, Electronic, Magnetic, and Hydrogen Adsorption Properties. J Phys Chem A 2010; 114:5049-57. [DOI: 10.1021/jp100459c] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
| | - Royoji Sahara
- Institute for Materials Research (IMR), 2-1-1, Katahira, Aoba-Ku, Sendai 980 8577, Japan
| | - Hiroshi Mizuseki
- Institute for Materials Research (IMR), 2-1-1, Katahira, Aoba-Ku, Sendai 980 8577, Japan
| | - Yoshiyuki Kawazoe
- Institute for Materials Research (IMR), 2-1-1, Katahira, Aoba-Ku, Sendai 980 8577, Japan
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12
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Höltzl T, Veldeman N, De Haeck J, Veszprémi T, Lievens P, Nguyen MT. Growth mechanism and chemical bonding in scandium-doped copper clusters: experimental and theoretical study in concert. Chemistry 2009; 15:3970-82. [PMID: 19296484 DOI: 10.1002/chem.200802372] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Size matters! The electronic structure and size-dependent stability of neutral and cationic scandium-doped copper clusters have been investigated by mass spectrometric studies (for the cations) and also quantum chemical computations. The proposed reaction paths ultimately lead to the most stable Frank-Kasper-shaped Cu(16)Sc(+) cluster (shown here), which could be the germ of a new crystallization process.Electronic structure and size-dependent stability of scandium-doped copper cluster cations, Cu(n)Sc(+), were investigated by using a dual-target dual-laser vaporization production scheme followed by mass spectrometric studies and also quantum chemical computations in the density functional theory framework. The neutral species also were studied by using computational methods. Enhanced abundances and dissociation energies were measured in the case of Cu(n)Sc(+) for n=4, 6, 8, 10 and 16, the last of these identified as being extraordinary stable. Neutral clusters are stable with n=5, 7, 9 and 15, which are isoelectronic with respect to the number of the valence s electrons with the stable cationic clusters; hence a simple electron count determines cluster properties to a great extent. The Cu(17)Sc cluster was found to be a superatomic molecule, containing Cu(16)Sc(+) and Cu(-) units; however, the charge separation is not as pronounced as in the case of CuLi. Cu(15)Sc was found to be a stable cluster with a large dissociation energy and a closed electronic structure; hence this can be regarded as a superatom, analogous to the noble gases. The main factors determining the growth patterns of these clusters are the central position of the scandium atom and the successive filling of the shell orbitals. For smaller clusters, the reaction paths appear to diverge yielding various products; however all paths ultimately lead to the most stable Frank-Kasper shaped Cu(16)Sc cluster, which in turn can be the germ of the crystallization process.
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Affiliation(s)
- Tibor Höltzl
- Department of Chemistry and INPAC-Institute for Nanoscale Physics and Chemistry, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
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