Spin–Orbit Coupling Effects in AumPtn Clusters (m + n = 4)

Moreno, Norberto; Ferraro, Franklin; Flórez, Elizabeth; Hadad, C. Z.; Restrepo, Albeiro

doi:10.1021/acs.jpca.5b11397

Cited by 11 publications

(8 citation statements)

References 65 publications

(97 reference statements)

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“…Contrary to the case of the isolated AB molecule, in which only one geometrical shape is possible, and in which the conformational isomerism does not introduce differences for the interaction with the catalyst, in the case of Au 4 it is necessary to pay special attention to properly locate its lowest energy configurations. In fact, for Au 4 there are two different geometrical motifs, very close in energy to each other (see Figure A) . The global minimum corresponds to a D 2h rhomboid‐like geometry, and the second most stable geometry to a C 2v Y‐like geometry, at only 0.041 eV above; both structures at singlet spin state.…”

Section: Methodsmentioning

confidence: 81%

“…In this work, we offer a computational study to contribute in the answer of these questions by using neutral gold tetramer as a representative cluster. Au 4 has the advantage of being a much‐studied system from theoretical and experimental point of views . For example, it has been used as a viable and representative model of supported small clusters for dehydrogenation reactions .…”

Section: Introductionmentioning

confidence: 99%

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Activation and diffusion of ammonia borane hydrogen on gold tetramers

Mejía

Ferraro

Osorio

et al. 2017

Int J of Quantum Chemistry

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One of the most serious candidates for safe storage of high hydrogen densities is ammonia borane, AB. Likewise, one of the most versatile catalysts known is gold in the form of atomic clusters. Taking these elements into account, in this work a density functional theory -based study about initial activation, detachment, and diffusion of ammonia borane hydrogen on gold tetramer, as a catalyst model, is developed. It was found that the total process is exergonic and that the hydrogen diffusion occurs with very low energy barriers. The process has a hydrogen detachment energy barrier lower than the one of the uncatalyzed AB, and that is easily overcome by the energy expelled in the previous stage of formation of the initial activated species. Additionally, all the process is assisted by the fluxionality of the gold cluster, and occurs via a unique catalytically activated initial species, which contains a three-center simultaneous interaction at the catalytically activated zone.ammonia borane, gold cluster catalyst, gold-fluxionality, theoretical study, three-center bonding | I N TR ODU C TI ONResearch about new ways for practical, safe, and economically convenient storage and release of large quantities of hydrogen in small volumes is today a very important issue. [1,2] Hydrogen has an energy content by mass almost three times superior to petroleum, [3] is the most abundant substance in the universe, is source-independent, and its combustion product, water, is environmentally friendly. Additionally, the availability of activated hydrogen is highly relevant for a large number of reactions in the chemical industry, where reduction or hydrogenation are necessary steps. [4,5] Among lightweight hydrogen storage materials, ammonia borane, AB (H 3 BNH 3 ), is a substance that contains large amounts of hydrogen (a total of 19.6 wt.%), [3] which is relatively easy to extract, either by direct or by assisted thermolysis, [6,7] by catalyzed room temperature solvolysis, [3,[8][9][10][11] or by other methods. [12][13][14][15] Additionally, AB can be easily and safely transported, [16] because, on the one hand, is a relatively stable solid at room conditions, [3,6,16] and is a substance soluble in many solvents, such as water, methanol, and tetraglyme. [3,[8][9][10][11][12] It has been found that the use of transition metals as catalysts in the AB dehydrogenation has the advantage of avoiding the expenditure of large amounts of energy, necessary for the hydrogen release. [7,[16][17][18] Even, in some cases, the catalysis has emerged as a solution to diminish the unwanted by-products of hydrogen release. [10,12,18] Transition metals of different nature, both noble and non-noble, as well as binary or tertiary combinations among them, have shown catalytic activity toward the extraction of hydrogen from AB. [3,[8][9][10][11][12]17,18] In the case of nanoparticles, the studies show that although some transition metals are better than others, the decrease in size (within certain limits and conditions [19] ) of the nanoparticles of the ...

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Section: Methodsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Activation and diffusion of ammonia borane hydrogen on gold tetramers

Mejía

Ferraro

Osorio

et al. 2017

Int J of Quantum Chemistry

Self Cite

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“…The compatibility relationship between the D ∞h and D ∞h * point groups, resulting from the product between the spin‐irrep (γ 1/2 ) and the each single‐groups irreps, is given in Table . The role of the spin‐orbit coupling in gold‐clusters has been accounted for I h / O h ‐[Au 13 ] and the 18‐ ve cluster W@Au 12 , among other superatomic clusters, where the 1P 6 and 1D 10 superatomic shells split into 1

{normalP}_{1 / 2}^{2}

⊕1

{normalP}_{3 / 2}^{4}

and 1

{normalD}_{3 / 2}^{4}

⊕1

{normalD}_{5 / 2}^{6}

, respectively.…”

Section: Resultsmentioning

confidence: 99%

A superatomic molecule under the spin‐orbit coupling: Insights from the electronic properties in the thiolate‐protected Au₃₈(SR)₂₄ cluster

Muñoz-Castro

2017

Int J of Quantum Chemistry

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The role of the spin-orbit coupling in Au 38 (SR) 24 , as a representative case for a superatomic molecules is studied to offer a complete view of the relativistic effect in heavy elements clusters. Its Au 91 23 core can be described in as an analog to a diatomic molecule, such as F 2 , allowing the electronic structure to be depicted in terms of the D 1h point group. First, we showed the electronic structure under the spin-orbit framework using total angular momentum representations (j 5 ' 6 s; spinors), which allows us to characterize the expected splitting of certain levels derived from the cluster core. Accordingly, the optical properties are evaluated under spin-orbit coupling regime, revealing differences in the low-energy region of the absorption spectrum. Lastly, the variation of electron affinity (EA) and ionization potential (IP) properties is evaluated. This reveals characteristic consequences of the inclusion of spin-orbit coupling in Au 38 (SR) 24 , as a bridge to larger thiolateprotected gold clusters.double-groups, gold clusters, relativistic, spin-orbit, superatoms 1 | I N TR ODU C TI ON Gold nanoclusters have attracted much attention owing to their potential in interdisciplinary applications of technological interest, such as in chemical and biomedical issues. [1][2][3][4][5][6][7][8][9][10] The development of efficient synthetic and purification procedures enables us to obtain atomically precise novel metal clusters denoting differences in geometrical and electronic structures, unraveling size-dependent properties. This prompts the further understanding of gold clusters [11][12][13][14][15][16][17][18][19] to expand knowledge related to the development of clusters displaying special electronic, structural, and optical and catalytic properties. [20][21][22] A particularly interesting class of gold nanoparticles is displayed by thiolate protected (-SR) structures, where great advances have been achieved over the last two decades. In this concern, structural and optical properties has been well explored, [17,[23][24][25] reflecting the inherent relationship between geometric and electronic structure. Au 25 (SR) 18 and Au 38 (SR) 25 are two prototypical examples for thiolate protected clusters, which can be considered as a central core embedded in a structural protecting layer. [11,18] This approach is useful to rationalize their stability in terms of the electronic requirements from the core pursuing a closed-shell configuration.The characterized structure for [Au 25 (SR) 18 ]can be viewed as a central filled icosahedral Au 13 cage, or core, surrounded (or protected), by six Au 3 (SR) 2 staple motifs. [26] According to the divide-and-protect approach, in line with the electron count rules given by Häkkinen and coworkers, [11,18] the Au 13 core formally exhibits a 15 charge leading to a 8-valence electron (ve) cluster. The resulting [Au 13 ] 51 core, with its 1S 2 1P 6 electronic configuration, is able to mimic the behavior of isolated atoms, [27] and thus is coined as a superatom, similar to other ...

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“…NPs have been experimentally studied for the potential applications in the nanotechnology, material science, biology, and medicine in the past decade, because of their catalytic activity. [11][12][13][14][15][16][17] For instance, the interactions between neutral Au [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] NPs and O 2 molecule were studied by Woodham et al [18,19] The oxygen on the NPs is highly activated. In addition, the studies of Au 19 Ag and AuAg 19 NPs with O 2 show that the adsorption energies of O 2 on the NPs increase in the following order: Au 20 < Au 19 Ag < Ag 19 Au Ag 20 because of the different chemical environments of adsorbed O 2 , depending on the structures and components of the silver and gold NPs.…”

mentioning

confidence: 99%

“…[20] Theoretical calculations of NPs also can help to provide valuable insights for developing new nanomaterials and nanotechnologies. [21][22][23][24][25][26][27][28][29][30][31][32][33][34] First principle calculations suggest that TM atoms in the Au n M NPs (n 7, M 5 Ni, Pd, and Pt) change their geometries and electronic properties of original pure gold NPs drastically. [29] The effects of dopant atoms are also found in Au n Pd (n 5 1-4), [30] Au n La (n 5 1-8), [31] and Au n Si (n 5 1-8) [32] NPs.…”

mentioning

confidence: 99%