Готові списки джерел за темами / Metal Clusters - Structures - Computational Study

Добірка наукової літератури з теми "Metal Clusters - Structures - Computational Study"

Автор: Grafiati

Опубліковано: 7 вересня 2023

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Статті в журналах з теми "Metal Clusters - Structures - Computational Study"

BORRMANN, PETER, BERND DIEKMANN, EBERHARD R. HILF, and DAVID TOMÁNEK. "MAGNETISM OF SMALL TRANSITION-METAL CLUSTERS AND EFFECTS OF ISOMERIZATION." Surface Review and Letters 03, no. 01 (February 1996): 463–66. http://dx.doi.org/10.1142/s0218625x96000838.

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We investigate the magnetic properties of small transition-metal clusters using a simple statistical model, which requires some input data from ab-initio spin-density-functional calculations. In our study, we consider a thermodynamically equilibrated ensemble of clusters with different structures, spin multiplicities, and ground-state energies. We calculate the physical properties of this system by weighting the individual configurations according to the Boltzmann statistics. We find that presence of isomers with very similar ground-state energies, yet very different magnetic properties, gives rise to a rich magnetic behavior of the system which differs significantly from what would be expected for single configurations. We apply the present model to determine the magnetic susceptibility of a cluster ensemble of Langevin paramagnets. Our results show that some of the anomalies in the magnetic behavior of transition-metal clusters might be understood in the framework of our model which is, of course, limited by the extremely high computational effort needed to obtain the input data.

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Fotopoulos, Vasileios, David Mora-Fonz, Manuel Kleinbichler, Rishi Bodlos, Ernst Kozeschnik, Lorenz Romaner, and Alexander L. Shluger. "Structure and Migration Mechanisms of Small Vacancy Clusters in Cu: A Combined EAM and DFT Study." Nanomaterials 13, no. 9 (April 25, 2023): 1464. http://dx.doi.org/10.3390/nano13091464.

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Voids in face-centered cubic (fcc) metals are commonly assumed to form via the aggregation of vacancies; however, the mechanisms of vacancy clustering and diffusion are not fully understood. In this study, we use computational modeling to provide a detailed insight into the structures and formation energies of primary vacancy clusters, mechanisms and barriers for their migration in bulk copper, and how these properties are affected at simple grain boundaries. The calculations were carried out using embedded atom method (EAM) potentials and density functional theory (DFT) and employed the site-occupation disorder code (SOD), the activation relaxation technique nouveau (ARTn) and the knowledge led master code (KLMC). We investigate stable structures and migration paths and barriers for clusters of up to six vacancies. The migration of vacancy clusters occurs via hops of individual constituent vacancies with di-vacancies having a significantly smaller migration barrier than mono-vacancies and other clusters. This barrier is further reduced when di-vacancies interact with grain boundaries. This interaction leads to the formation of self-interstitial atoms and introduces significant changes into the boundary structure. Tetra-, penta-, and hexa-vacancy clusters exhibit increasingly complex migration paths and higher barriers than smaller clusters. Finally, a direct comparison with the DFT results shows that EAM can accurately describe the vacancy-induced relaxation effects in the Cu bulk and in grain boundaries. Significant discrepancies between the two methods were found in structures with a higher number of low-coordinated atoms, such as penta-vacancies and di-vacancy absortion by grain boundary. These results will be useful for modeling the mechanisms of diffusion of complex defect structures and provide further insights into the structural evolution of metal films under thermal and mechanical stress.

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Marques, J. M. C., F. B. Pereira, J. L. Llanio-Trujillo, P. E. Abreu, M. Albertí, A. Aguilar, F. Pirani, and M. Bartolomei. "A global optimization perspective on molecular clusters." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2092 (March 20, 2017): 20160198. http://dx.doi.org/10.1098/rsta.2016.0198.

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Although there is a long history behind the idea of chemical structure, this is a key concept that continues to challenge chemists. Chemical structure is fundamental to understanding most of the properties of matter and its knowledge for complex systems requires the use of state-of-the-art techniques, either experimental or theoretical. From the theoretical view point, one needs to establish the interaction potential among the atoms or molecules of the system, which contains all the information regarding the energy landscape, and employ optimization algorithms to discover the relevant stationary points. In particular, global optimization methods are of major importance to search for the low-energy structures of molecular aggregates. We review the application of global optimization techniques to several molecular clusters; some new results are also reported. Emphasis is given to evolutionary algorithms and their application in the study of the microsolvation of alkali-metal and Ca 2+ ions with various types of solvents. This article is part of the themed issue ‘Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces’.

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Ngan, Vu Thi, Philipp Gruene, Pieterjan Claes, Ewald Janssens, André Fielicke, Minh Tho Nguyen, and Peter Lievens. "Disparate Effects of Cu and V on Structures of Exohedral Transition Metal-Doped Silicon Clusters: A Combined Far-Infrared Spectroscopic and Computational Study." Journal of the American Chemical Society 132, no. 44 (November 10, 2010): 15589–602. http://dx.doi.org/10.1021/ja105099u.

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Catlow, C. R. A., S. A. French, A. A. Sokol, and J. M. Thomas. "Computational approaches to the determination of active site structures and reaction mechanisms in heterogeneous catalysts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1829 (April 15, 2005): 913–36. http://dx.doi.org/10.1098/rsta.2004.1529.

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We apply quantum chemical methods to the study of active site structures and reaction mechanisms in mesoporous silica and metal oxide catalysts. Our approach is based on the use of both molecular cluster and embedded cluster (QM/MM) techniques, where the active site and molecular complex are described using density functional theory (DFT) and the embedding matrix simulated by shell model potentials. We consider three case studies: alkene epoxidation over the microporous TS-1 catalyst; methanol synthesis on ZnO and Cu/ZnO and C–H bond activation over Li-doped MgO.

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LOPES, JULIANA FEDOCE, JÚLIO C. S. DA SILVA, WILLIAN R. ROCHA, WAGNER B. DE ALMEIDA, and HÉLIO F. DOS SANTOS. "QUANTUM CHEMICAL STUDY OF CISPLATIN-WATER COMPLEXES: AN INVESTIGATION OF ELECTRON CORRELATION EFFECTS." Journal of Theoretical and Computational Chemistry 10, no. 03 (June 2011): 371–91. http://dx.doi.org/10.1142/s0219633611006517.

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The interaction of cisplatin ([ Pt(NH3)2Cl2] ) with water was studied for distinct complexation modes aiming to investigate the level of calculation required to describe transition metal complexes of biological relevance, where large scale ab initio post-Hartree-Fock calculations are usually precluded. Coupled Cluster (CCSD(T)) single point calculations employing MP2 and MP4(SDQ) optimized geometries and good quality basis sets, using effective core potential for platinum atom, are reported as well as Density Functional Theory (DFT) results employing various exchange-correlation functional. The importance of electron correlation effects for the calculation of interaction energies is discussed. The extension of correlation energy recovered by DFT was assessed considering the CCSD(T) results as reference. The recently developed M06-2x functional showed the best overall agreement with CCSD(T) calculations. The relative importance of the electrostatic and dispersion contributions to the interaction energy was estimated with the aid of the atoms in molecules theory and also using an empirical approach based on the multipole expansion method. It was found a strong dependence of the energy contributions on the spatial orientation of water and cisplatin monomers, with the electrostatic contribution dominating the interaction energy for the lowest energy equilibrium structures.

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Zhao, Run-Ning, Yanhong Yuan, and Ju-Guang Han. "Transition metal Mo-doped boron clusters: A computational investigation." Journal of Theoretical and Computational Chemistry 13, no. 05 (August 2014): 1450036. http://dx.doi.org/10.1142/s0219633614500369.

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Geometries associated with relative stabilities and energy gaps of the Mo -doped boron clusters have been investigated systematically by using density functional theory. The critical size of Mo -encapsulated B n structures emerges as n = 10, the evaluated relative stabilities in term of the calculated fragmentation energies reveal that the MoB 6 has enhanced stabilities over their neighboring clusters. Furthermore, the calculated polarities of the MoB n reveal that the hypercoordinated planar MoB 10 wheel is a weakened polar molecule and MoB 11 ring is a nonpolar molecule, and aromatic properties are discussed. Additionally, the MoB 10 cluster with smaller highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap is supposed to be stronger chemical activity and smaller chemical hardness. Moreover, the recorded natural populations show that the charges transfer from boron framework to Mo atom. It should be pointed out that the remarkable charge-transfer features of MoB n clusters are distinctly similar to those of transitional metal (TM)-doped Si n clusters; growth-pattern of the TMBn depends on the doped TM impurity.

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Addicoat, Matthew A., and Gregory F. Metha. "Computational Study of CO Reactivity with Nb3X Heteronuclear Clusters." Australian Journal of Chemistry 61, no. 11 (2008): 854. http://dx.doi.org/10.1071/ch08269.

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Density functional calculations were performed to determine the equilibrium structures, ionization potentials, and electron affinities of Nb3X clusters (X = Na, Al, Sc, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd). Pseudo-tetrahedral geometries were preferred for all Nb3X clusters except Nb3Cd. The equilibrium structures and binding energies of the associatively and dissociatively bound products of the Nb3X + CO reaction were calculated at the same level of theory. All clusters were found to thermodynamically dissociate CO. Only Nb3Al and Nb3Cd reduced the enthalpy of dissociation relative to Nb4, whereas all other heteroatoms increased it.

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Chen, Sian, Haining Wang, Shanfu Lu, and Yan Xiang. "Monolayer MoS2 film supported metal electrocatalysts: a DFT study." RSC Advances 6, no. 109 (2016): 107836–39. http://dx.doi.org/10.1039/c6ra23995a.

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Álvarez-Zapatero, Pablo, and Andrés Aguado. "Computational characterisation of structure and metallicity in small neutral and singly-charged cadmium clusters." Physical Chemistry Chemical Physics 21, no. 23 (2019): 12321–34. http://dx.doi.org/10.1039/c9cp01814j.

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Putative global minimum structures and an analysis of the electronic structure of neutral and charged cadmium clusters are reported to gain insight into the gradual insulator-to-metal transition in the small-size regime.

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Більше джерел

Дисертації з теми "Metal Clusters - Structures - Computational Study"

Fernández, Villanueva Estefanía. "Theoretical Study of the Geometrical, Electronic and Catalytic properties of Metal Clusters and Nanoparticles." Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/135277.

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[ES] Dado su tamaño subnanométrico, los clusters metálicos están regidos por el confinamiento cuántico, lo que les hace más "moleculares" y menos "metálicos". En consecuencia, manifiestan propiedades que difieren con respecto a las de partículas más grandes del mismo elemento, y que a menudo son ventajosas para la catálisis de reacciones específicas. Además, su menor tamaño los hace más económicos, con una mayor superficie expuesta. Todo ello hace que los clusters sean opciones muy interesantes en catálisis, y su estudio, síntesis y aplicación ha crecido continuamente desde su descubrimiento en los años 90. Esta tesis se ha centrado principalmente en el cobre, del que se presenta, en primer lugar, un estudio fundamental sobre la disociación de oxígeno por clusters de diferentes tamaños. Después, se explora computacionalmente la catálisis de las oxidaciones de CO y propeno, confirmando que los clusters de Cu5 (o inferior) son prometedores para reacciones de oxidación. Las dos reacciones utilizadas son buenos ejemplos de la aplicación potencial en industria, sea para reducir emisiones de CO o para producir epóxido de propeno, que es un intermedio importante en la producción de plásticos y adhesivos, entre otros. Además, también se estudió la influencia de dos soportes en los clusters de cobre y su capacidad de oxidación: N-grafeno como un sistema más inerte y ceria como uno que puede participar activamente en reacciones de oxidación. Finalmente, se incluyen otros dos estudios más específicos, sobre la capacidad de los clusters de Pt3 y Pd3 para catalizar reaciones de acoplamiento C-C como la reacción de Heck, importante para la síntesis de productos de la química fina, y sobre la reacción CO + NO en clusters de Pt, motivado por su uso potencial como catalizadores para la conversión de esas especies en los menos perjudiciales CO2 y N2 en motores de combustión interna.
[CAT] Atès que són de grandària subnanomètrica, els clusters metàl·lics estan regits pel confinament quàntic, el qual els fa més "moleculars" i menys "metàl·lics". En conseqüència, manifesten propietats que són diferents a les de partícules més grans del mateix element, i que sovint són avantatjoses per a la catàlisi de reaccions específiques. A més a més, la seua menor grandària fa que siguen més econòmics, amb una major superfície exposada. Així, els clusters són una opció molt interesant en catàlisi, i el seu estudi, síntesi i aplicació ha cres-cut contínuament des del seu descobriment als anys 90. Aquesta tesi s'ha centrat principalment en el coure, del qual es presenta, en primer lloc, un estudi fonamental sobre la dissociació de l'oxígen per clusters de diferents grandàries. Després, s'explora computacionalment la catàlisi de les oxidacions de CO i de propè, confirmant que els clusters de Cu5 (o inferior) són prometedors per a reaccions d'oxidació. Les dues reaccions utilitzades són bons exemples de l'aplicació potencial en indústria, siga per reduir emissions de CO o per produir epòxid de propè, que és un intermedi important en la producció de plàstics i adhesius, entre altres. A més, també es va estudiar la influència de dos suports en els clusters de coure i la seua capacitat d'oxidació: N-grafè com a un sistema més inert i cèria com a un que pot participar activament en reaccions d'oxidació. Finalment, s'inclouen altres dos estudis més específics, sobre la capacitat dels clusters de Pt3 y Pd3 per catalitzar reaccions d'acoblament C-C com la reacció de Heck, important per a la síntesi de productes de la química fina, i sobre la reacció CO + NO als clusters de Pt, motivat pel seu ús potencial com a catalitzadors per a la conversió d'eixes espècies en els menys perjudicials CO2 i N2 als motors de combustió interna.
[EN] Due to their subnanometric size, metal clusters belong to the regime affected by quantum confinement, which makes them more "molecular" and less "metallic". As a result, they exhibit properties that differ with respect to those of larger particles of the same element, and which are often advantageous in the catalysis of specific reactions. Besides, their smaller size makes them more economic and with a higher surface exposed. All of this renders metal clusters very interesting options for catalysis, and their study, synthesis and application has steadily increased since their discovery in the 90s. In this work we have largely focused on copper, of which a fundamental study on the oxygen dissociation by clusters of different sizes is first presented. Then, the catalysis of the CO and propene oxidation reactions is theoretically explored, confirming that Cu5 (or smaller) clusters are promising systems for oxidation reactions. The two reactions used are good examples of the potential application in industry, either to reduce CO emissions or to produce propene epoxide, an important intermediate in the production of plastics and adhesives, among others. In addition, the influence of two supports in the copper clusters and their oxidation capability is explored: on N-graphene as a more inert system and on ceria as one that can actively participate in oxidation reactions. Finally, two other more specific studies are included, regarding the capability of Pt3 and Pd3 clusters to undergo C-C coupling reactions such as the Heck reaction, important for the synthesis of many products of fine chemistry, and regarding the CO + NO reaction on Pt clusters, motivated by their potential use as catalysts for the conversion of those species in less harmful CO2 and N2 in internal combustion engines.
En primer lugar me gustaría agradecer al Ministerio de Economía y Competitividad de España (MINECO) por la financiación de esta tesis mediante el programa Severo Ochoa (SVP-2013-068146), incluyendo los costes adicionales de mi estancia de investigación (EEBB-I-17-12057).
Fernández Villanueva, E. (2019). Theoretical Study of the Geometrical, Electronic and Catalytic properties of Metal Clusters and Nanoparticles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135277
TESIS

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Wright, Nicholas David. "Development of computational methodologies for the study of metal complex structures." Thesis, University of Surrey, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.483973.

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Hu, Chao-Jie, and 胡朝捷. "Computational Study of Alkaline Earth Metal Atom on Ge11 and Ge12 Clusters." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/7q8qnz.

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Анотація:

碩士
中國文化大學
化學系應用化學碩士班
103
We have used the B3LYP of density functional theory (DFT) and a simple basis set 6-31G* to optimize the structures of the hybrid clusters formed by adsorptions of alkaline earth metal(AEM) on Ge11 and Ge12 . Generally, Be has the best capability of forming covalent bonds with Ge among Be、Mg、Ca. Geometric relaxations//single point energies were carried out at the B3LYP/6-31G*//B3LYP/6-311++G(3df) level; the same method was applied to transition-state search.Our results showed that Be is commonly hypervalent with MTV > 3, higher than the expected value 2, especially in those endohedrons. Hirshfeld charges(HCs) and molecular orbitals indicated that back-donation from hosts facilitated such hypervalency. In CaGe11 and CaGe12 ,Ca-Ge bonds have small Mayer bond orders(MBO) but metal adsorption energies (Ead) are higher than in MgGe11 and MgGe12 because MBOs underestimate the bond ionicities, which are revealed by the obviously positive HCs of Ca atoms. The binding energies (BE) in MGen are comparable with different M and the same n , meaning the contribution of metal adsorption is not significant to the complete dissociation, but the greater stability of Ge12 than Ge11 . However, Eads in MGen (also different M and same n) imply that Be adsorbs strongly on Gen, then in Ca, and then in Mg. Mg-Ge has less covalency than Be-Ge and less iconicity than Ca-Ge that make Mg the weakest adsorbate.

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Lu, Wei, and 呂瑋. "Computational Study of Alkaline Earth Metal Atom on Si7~Si9 Silicon Clusters." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39383810600961133729.

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Анотація:

碩士
中國文化大學
應用化學研究所
98
In this these, geometric optimizations , single point energies, and HOMO-LUMO gap were calculated at the B3LYP/6-311++G(3df)groups, respectively. Total energies of all Sin and MSin clusters increase with n and metal size because as n increases number of electrons grows. However, if we look at the average binding energy which is relavent to cluster stability, we find that although stability still increases with n, BeSin and CaSin are more stable than MgSin at the same n. Form Hirshfeld changes, one knows that Be-Si bonds are very covalent while Ca-Si bonds are much move ionic, both effects result into lower-energy clusters. On the other hand, Mg-Si bond are less covalent and less ionic, hence MgSi clusters are the weakest ones. HOMO-LUMO gap is more complicated, it may be affected by covalency and iconicity, but in general BeSin have the highest valne than other hybrid clusters. Although Mayer bond order of Be-Si is the largests and Ca-Si is the smallest among M-Si bonds, BeSin and CaSin has very similar average binding energies, indicating MBO may underestimate the ionic contribution.

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Cheng, Jhao-Kai, and 程昭凱. "Computational Study of Alkaline Earth Metal Atom on Ge6~Ge8 Germanium Clusters." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/81849466643765111687.

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Анотація:

碩士
中國文化大學
應用化學研究所
99
In this thesis, we report some lowest-energy structures and the most stable state of alkaline earth metal (AEM) atom adsorbed on the small germanium cluster Ge6~Ge8 at the B3LYP/LANL2DZ level. We also investigated their HOMO-LUMO gaps, charge distribution, binding energies、Mayer Bond Orders and Mayer Total Valences. We compared with the above clusters with those of alkali metal atoms adsorbed on the surface of small germanium clusters and alkali metal atoms adsorbed on the anion group of small clusters of germanium surface(Ge6－~Ge8－), which is isoelectronic with the AEM-Gen(n=6~8)clusters. Our results reveal that BeGen are always the ones having the highest adsorption energy among add other hybrid clusters. Generally speaking, Be-Ge bonds and strong then other M-bonds and the bonding capacity of Be is at least one more single bond than the valence bond theory world predict. however, the stability of BeGen is still lower than Gen+1, which indicates that Ge-Ge bond is stronger then Gen+1, which indicates that Ge-Ge bond is stronger then Be-Ge bond. It looks like to be so because Ge, the 4A element, should have higher bonding capacity than Be, the 2A element. Also the relative atomic radii of Be and Ge count the relative bonding strength.

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Ho, Gong-Ming, and 何恭銘. "Computational Study of Alkaline Earth Metal Atom on Ge9 and Ge10 Germanium Clusters." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/37603607320627868032.

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Анотація:

碩士
中國文化大學
化學系應用化學碩士班
100
We have used the B3LYP density functional theory (DFT) and a simple basis set 6-31G* to optimize the structures of the hybrid clusters formed by adsorptions of alkaline earth metal (AEM) on Ge9 and Ge10. Generally, Be has the best capability of forming covalent bonds with Ge among Be、Mg、Ca. Such covalency is reflected in the trivially positive Hirshfeld charges (Hirshfield charge, HC) of Be atoms and large Mayer bond order (Mayer bond order, MBO) of Be-Ge bonds. The covalency decreases as metal atoms move down in the AEM group. In CaGe9 and CaGe10 , Ca-Ge bonds have small MBO but their metal adsorption energies (Ead) are higher than in MgGe9 and MgGe10 because MBOs underestimate the bond ionicity, which are revealed by the obviously positive HCs of Ca atoms. The binding energies (BE) in MGen are comparable with different M for the same n, meaning the contribution of metal adsorption is not significant to the complete dissociation into separated atoms and it is mainly due to the greater stability of Ge10 than Ge9 . However, Eads in MGen (also different M and same n) imply that Be adsorbs strongly on Gen, then in Ca, and then in Mg. Mg-Ge has less covalency than Be-Ge and less iconicity than Ca-Ge that make Mg the weakest adsorbate. The trends of metal HCs and MTVs are opposite with each other. Beside CaGe9 and CaGe10, the ΔEg, Ead, and BE of ground state BeGe9,10 and MgGe9,10 vary in the similar trend.

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Cantera, Lopez Homero. "Structural and electronic study of Silicon doped structures: Aggregates, Wires, and Bulk Systems." Doctoral thesis, 2011. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-201111238529.

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Recent experiments have shown that Ta@Si16+ is a very stable cation from which it should be possible to create Si-based cluster assembled materials. In this paper we have studied, by means of first-principles spin-dependent generalized gradient approximation calculations, the structural and electronic properties of the following systems: (i) Ta@Sin+ clusters in the range n = 14–18; (ii) (Ta@Si16F)m aggregates with sizes m = 1–8 formed by Ta@Si16F molecules; (iii) infinite wires formed by stacking triangular (Ta@Si16F)3 aggregates twisted 60◦ to each other along the vertical axis; and (iv) the fcc phase of bulk Ta@Si16F. The minimum-energy Ta@Si16+ cluster shows C3v symmetry, having 40 meV smaller total energy than a fullerenelike D4d isomer. However, the molecule Ta@Si16F formed with that D4d isomer is 40 meV more stable than that formed with the C3v one. We have optimized several [Ta@Si16F]n aggregates (n = 1–8) which contain the Ta@Si16 unit with D4d symmetry. The more bound (Ta@Si16F)6 aggregate is formed by stacking vertically two triangular (Ta@Si16F)3 aggregates which are twisted 60◦ to each other. The infinite wire formed with that (Ta@Si16F)6 aggregate as the unit cell has a cohesive energy 1.88 eV and a small highest occupied molecular orbital–lowest occupied molecular orbital gap. We have optimized also a metastable fcc bulk phase having the Ta@Si16F supermolecule as the unit cell. A Birch-Murnaghan fit to that phase produces a cohesive energy 0.84 eV at lattice constant 12.27 A, with bulk modulus 7.55 GPa and a phase stability to isotropic compression smaller than 0.75 GPa. That phase is nonmagnetic and shows a band gap of 0.20 eV. Using the values of hardness of Ta@Si16F molecules, we estimated a correction enhancement factor ∼3 to that small band gap. For that metastable solid we performed a 13.5-ps run of first-principles molecular dynamics annealing at 300 K and constant volume, and we found that the Ta@Si16F supermolecule in the fcc cell becomes severely distorted after the first 5 ps.

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Частини книг з теми "Metal Clusters - Structures - Computational Study"

Paz Borbón, Lauro Oliver. "Theoretical Study of Pd–Au Clusters." In Computational Studies of Transition Metal Nanoalloys, 103–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-18012-5_7.

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Ohnishi, S. "Electronic shell structures in aluminum and noble metal clusters." In Nuclear Physics Concepts in the Study of Atomic Cluster Physics, 312–17. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/3-540-55625-7_34.

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Das, Shayeri, Prabhat Ranjan, and Tanmoy Chakraborty. "A Computational Study of Metal Doped Silver Nanoparticle-Based Clusters." In Nanotechnology-Enhanced Solid Materials, 99–116. New York: Apple Academic Press, 2023. http://dx.doi.org/10.1201/9781003333449-5.

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Cao, Zexing. "Reactivity of Metal Carbene Clusters Pt n CH 2 + and PtMCH 2 + (M = Cu, Ag, Au, Pt, Rh) Toward O2 and NH3: A Computational Study." In Computational Organometallic Chemistry, 169–218. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-25258-7_7.

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Fujimoto, Kyoko, Leonardo M. Angelone, Sunder S. Rajan, and Maria Ida Iacono. "Simplifying the Numerical Human Model with k-means Clustering Method." In Brain and Human Body Modeling 2020, 261–70. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-45623-8_15.

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AbstractCurrently, the safety assessment of radio-frequency (RF) heating using computational modeling is limited by the available numerical models which are not patient specific. However, RF-induced heating depends on the physical characteristics of the patient. The numerical model generation is difficult due to the highly time-consuming segmentation process. Therefore, having fewer types of segmented structures simplifies the generation of numerical models and reduces computational burden as a result. In this study, we used the k-means clustering method to reduce the number of dielectric properties of an existing numerical model and investigated the resulting difference in specific absorption rate (SAR) with respect to the number of clusters.

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Chroneos, A. "Computational study of energy materials." In Metal Oxide-Based Thin Film Structures, 263–81. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-811166-6.00012-1.

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Yamanaka, S., M. Shoji, K. Koizumi, R. Takeda, Y. Kitagawa, H. Isobe, and K. Yamaguchi. "General spin orbital density functional study of transition metal clusters and complexes." In Trends and Perspectives in Modern Computational Science, 286–93. CRC Press, 2006. http://dx.doi.org/10.1201/b12251-21.

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Fron, Eduard. "Zeolites as Scaffolds for Metal Nanoclusters." In Advances in Geopolymer-Zeolite Composites - Synthesis and Characterization. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96876.

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This chapter critically reviews the studies related to structural and photophysical properties of metal clusters within zeolites matrices and summarizes the progress made in understanding the host-guest interactions. The goal is to provide useful insight into the nature of such interactions and experiments used in identifying the excited state dynamics and the reaction mechanisms leading to the emitting species. Especially interesting are the combined experimental and computational approaches used to elucidate the structures and electronic transition of clusters inside the cavity. Although a number of excellent research articles have been published in the last years they only cover rather specific areas like organic photochemistry, confinement, charge transfer, theoretical modeling or photostimulated luminescence.

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"Case Study: Conducting a Structural Scale Metal Forming Finite Element Analysis Starting from Electronics Structures Calculations Using ICME Tools." In Integrated Computational Materials Engineering (ICME) for Metals, 379–409. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118342664.ch9.

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Gagliardi, Mariacristina. "Relevance of Mesh Dimension Optimization, Geometry Simplification and Discretization Accuracy in the Study of Mechanical Behaviour of Bare Metal Stents." In Innovations in Data Methodologies and Computational Algorithms for Medical Applications, 263–77. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-4666-0282-3.ch016.

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In this paper, a set of analyses on the deployment of coronary stents by using a nonlinear finite element method is proposed. The author proposes a convergence test able to select the appropriate mesh dimension and a methodology to perform the simplification of structures composed of cyclically repeated units to reduce the number of degree of freedom and the analysis run time. A systematic study, based on the analysis of seven meshes for each model, is performed, gradually reducing the element dimension. In addition, geometric models are simplified considering symmetries; adequate boundary conditions are applied and verified based on the results obtained from analysis of the whole model.

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Тези доповідей конференцій з теми "Metal Clusters - Structures - Computational Study"

PALA, RAJ GANESH S., THANH N. TRUONG, and FENG LIU. "COMPUTATIONAL STUDY OF METAL ADSORPTION ON TiO2 (110) SURFACE." In Clusters and Nano-Assemblies - Physical and Biological Systems. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701879_0015.

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Van der Maelen, Juan F., and Santiago García-Granda. "A comparative topological study of different metal-metal and metal-ligand interactions in polynuclear organometallic clusters." In PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2010 (ICCMSE-2010). AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4906743.

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Misaizu, Fuminori, M. Abdul Latif, Jenna W. J. Wu, Ryoichi Moriyama, Motoyoshi Nakano, Kiichirou Koyasu, and Keijiro Ohshimo. "Structures of stable oxide cluster ions of first-row late transition metals: An ion mobility-mass spectrometric study." In PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2019 (ICCMSE-2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5137928.

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Wang, Yi, and Teik C. Lim. "An Experimental and Computational Study of the Dynamic Characteristics of Spot-Welded Sheet Metal Structures." In SAE 2001 World Congress. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2001. http://dx.doi.org/10.4271/2001-01-0431.

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Karamanis, P., R. Marchal, P. Carbonnierre, and C. Pouchan. "Is there any connection between the (Hyper) polarizabilities of the ground state structures of clusters and those of their low lying isomers? A case study of aluminum doped silicon clusters." In INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2009: (ICCMSE 2009). AIP, 2012. http://dx.doi.org/10.1063/1.4771786.

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Roberts, Kendric, and Yen-Lin Han. "Investigating Density Functional Theory’s Effectiveness in Studying Metal-Organic Frameworks Structures." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11013.

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Abstract In combatting human induced climate change, carbon capture provides the potential to more slowly ease away from the dependence on hydrocarbon fuel sources, while mitigating the amount of CO2 released into the atmosphere. One promising material to use is metal-organic frameworks (MOF’s). MOF’s offer an immense variety in potential exceptionally porous structures, a property important in separation. As a result of practical experimental measurements being expensive and time consuming, interest in accomplishing the same goal through modeling has also increased. Using density functional theory to optimize the approximate experimentally measured atomic geometries has been shown to have sufficient accuracy. A previous study by Nazarian et al. was performed to optimize structures on the CoRE MOF Database using a supercomputer. The purpose of this study was to attempt to replicate their work done with a single MOF using computational resources more commonly available. Furthermore, as time tends to be the limiting factor in conducting these studies, the use of a smearing function was adjusted for two optimizations to see if any considerable improvement on the efficiency of the optimizations could be made. Our results show both optimizations improved the bond length accuracy relative to the raw data compared with the optimization from Nazarian, et al. The optimization with a more present smearing effect was able to converge the electron field in roughly half the time, while still showing nearly the same results, except for slightly more variability in the bond lengths involving transition metals. Unfortunately, the improvement in bond length, did not correspond in consistent improvement of the larger cell defining metrics. This shows that either a different energy minimum was found or the relationship between the larger cell parameters, with the more local parameters such as bond length is too complex for the method to effectively solve.

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Mun, Jiwon, Jaehyung Ju, Byoung-Gwan Yun, Byung-Moon Chang, and Doo-Man Kim. "A Numerical Study of a Molten Aluminum for Investment Casting of 3D Cellular Metals." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62847.

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Investment casting processes are influenced by a variety of parameters. Many researches considering viscosity as a constant have been conducted up to this point. In particular, however, viscosity with temperature change has not been much accounted for solidification and heat transfer simulation of molten metal in the investment casting process. In addition, analysis of behavior of metal flow as well as air gap problems for complex network structures have not been investigated much. The aim of this study is to build transient metal flow and velocity profile models considering temperature dependent viscosity in investment casting processes of cellular structures. In this study, a Computational Fluid Dynamics (CFD) modeling tool was used for metal flow and velocity profile in investment casting processing using User Defined Function (UDF) for temperature dependent viscosity. The results of the metal flow and velocity profile inside of the simple cylindrical geometry are represented. It is shown that for the validation of the numerical simulation, the velocity profile between analytical and numerical approaches showed very good agreement. Analytical approaches showed that velocity was reduced with the increase in viscosity, which is applied as a function of temperature. In particular, rapid decreasing in velocity was shown from under the melting temperature of the molten metal. There was no movement on metal flow at the room temperature. Numerical approaches showed that the liquid metal began to be solidified from the wall surface inside of the mold. For the same simulation time, it was shown that the metal flow in a cylinder that has 1mm diameter showed better fluidity rather than that of the cylinder that has 2mm diameter due to the increase in adhesion between liquid metal and the surface of the mold and surface tension between molten metal and air. The effective diameter by solidification is decreased with the time change.

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Storheim, Martin, Hagbart Alsos, Odd Sture Hopperstad, and Jørgen Amdahl. "An Extension of the BWH Instability Criterion: Numerical Study." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41178.

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The BWH criterion for simulating instability prior to necking in sheet metal has been extended with a post-necking damage model, in which the effect of the local neck inside a large element is accounted for with low mesh dependency. The model is incorporated in the explicit FE code LS-DYNA. The material model can be calibrated from a single uniaxial tensile test, and gives good prediction of rupture for a range of stress triaxialities. This paper investigates the robustness of the criterion through numerical simulations of different experiments, from forming limit tests to large impact experiments on stiffened panel structures. A full-scale collision is simulated with two different mesh-sizes to investigate the robustness of the fracture prediction. The validation cases are simulated with good accuracy considering the coarse meshes involved. Based on the validation, the post-necking extension of the BWH criterion can readily be used for structural design of offshore structures in order to assess the technical safety level of the structure against collisions in all phases of the design process. The method has a good ratio of accuracy vs. computational cost, and is less prone to user-errors as the calibration is simple and the mesh-scaling is automated.

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Nelson, Bryan, and Yann Quéméner. "Fatigue Life Analysis of Offshore Wind Turbine Support Structures in an Offshore Wind Farm." In ASME 2018 1st International Offshore Wind Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/iowtc2018-1061.

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This study evaluated, by time-domain simulations, the fatigue lives of several jacket support structures for 4 MW wind turbines distributed throughout an offshore wind farm off Taiwan’s west coast. An in-house RANS-based wind farm analysis tool, WiFa3D, has been developed to determine the effects of the wind turbine wake behaviour on the flow fields through wind farm clusters. To reduce computational cost, WiFa3D employs actuator disk models to simulate the body forces imposed on the flow field by the target wind turbines, where the actuator disk is defined by the swept region of the rotor in space, and a body force distribution representing the aerodynamic characteristics of the rotor is assigned within this virtual disk. Simulations were performed for a range of environmental conditions, which were then combined with preliminary site survey metocean data to produce a long-term statistical environment. The short-term environmental loads on the wind turbine rotors were calculated by an unsteady blade element momentum (BEM) model of the target 4 MW wind turbines. The fatigue assessment of the jacket support structure was then conducted by applying the Rainflow Counting scheme on the hot spot stresses variations, as read-out from Finite Element results, and by employing appropriate SN curves. The fatigue lives of several wind turbine support structures taken at various locations in the wind farm showed significant variations with the preliminary design condition that assumed a single wind turbine without wake disturbance from other units.

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Hussary, N. A., and J. V. R. Heberlein. "Primary Breakup of Metal in the Wire Arc Spray Process." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1023.

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Abstract The significance of metal atomization in the wire arc spray process is directly related to the final coating quality produced. Since the early observations of the melting behavior of the wire tips by Steffens, relatively little has been done to further the understanding of the mechanisms involved. The primary atomization of the molten wire tips show existence of sheets and extrusions on both electrodes which are strongly dependent on the system operating parameters. High-speed imaging has been used in this study, for classification of sheet, membrane and extrusion formations as a function of atomizing gas pressure, voltage and current settings. The breakup of metal structures formed on the electrodes is further classified in a manner consistent with established classifications for the break-up of other liquids, e.g. water or fuel. Quantitative descriptions of metal sheet lengths and breakup times are presented. The improved understanding of the metal breakup mechanisms in the wire arc spray process may provide a basis for (a) modification of existing computational codes for prediction of particle sizes and trajectories, and (b) for modifications to torch designs for providing more uniform particle fluxes.

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