Theory of bonding in transition-metal carbides and nitrides

Häglund, J.; Guillermet, F. Fernandez; Grimvall, Göran; Körling, M.

doi:10.1103/physrevb.48.11685

Cited by 444 publications

(260 citation statements)

References 24 publications

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“…The lattice constants of pure elements were previously calculated with first principles proposed [17] 4.9506 AEAEAE AEAEAE [19] Basic and Applied Research: Section I by Wang et al [17] It is clear that the results obtained in the present calculation are in good agreement with Wang et al [17] The lattice constants of pure elements obtained from experiments [18,19] are also listed in Table 1. The calculated values agree reasonably well with the experimental data.…”

Section: Resultssupporting

confidence: 79%

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

Long

Tao

Liu

et al. 2009

J. Phase Equilib. Diffus.

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Thermodynamic assessment of the Pt-Pb binary system has been performed by combining firstprinciple calculations with the CALPHAD method. The formation enthalpies of the Pt 3 Pb and PtPb 4 were calculated by using the projector-augmented-wave (PAW) method within the generalized gradient approximation (GGA). The CALPHAD assessment of the Pt-Pb system was then performed. The solution phases (liquid and fcc) were treated as substitutional solutions, the excess Gibbs energies of which were modeled using the Redlich-Kister polynomial. The three intermetallic compounds, Pt 3 Pb, PtPb, and PtPb 4 , were described as stoichiometric phases. Thermodynamic parameters of all the phases were optimized, which reproduces the most experimental data.

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Section: Resultssupporting

confidence: 79%

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

Long

Tao

Liu

et al. 2009

J. Phase Equilib. Diffus.

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“…8,14,15,18,25 In these materials, the chemical bonding exhibits a mixed character. 25,[30][31][32][33] For example, the valence bands of VC show a strong hybridization of the V͑3d͒ and C͑2p͒ states as expected for a covalent compound, 25,31 but there is, nevertheless, a rather large degree of ionicity in the V -C bonds with a positive Mulliken charge of ϳ1e on the V atoms. 25 Among the carbides, the magnitude of the metal→ carbon charge transfer increases following the VC Ͻ TiC Ͻ ZrC Ͻ TaC sequence, and there can be large variations in the relative density of the C͑2p͒ and metal nd states near the Fermi level.…”

Section: Introductionmentioning

confidence: 99%

Interaction of oxygen with ZrC(001) and VC(001): Photoemission and first-principles studies

et al. 2005

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High-resolution photoemission and first-principles density-functional calculations were used to study the interaction of oxygen with ZrC͑001͒ and VC͑001͒ surfaces. Atomic oxygen is present on the carbide substrates after small doses of O 2 at room temperature. At 500 K, the oxidation of the surfaces is fast and clear features for ZrO x or VO x are seen in the O͑1s͒, Zr͑3d͒, and V͑2p 3/2 ͒ core levels spectra, with an increase in the metal/carbon ratio of the samples. A big positive shift ͑1.3-1.6 eV͒ was detected for the C 1s core level in O / ZrC͑001͒, indicating the existence of strong O ↔ C or C↔ C interactions. A phenomenon corroborated by the results of first-principles calculations, which show a CZrZr hollow as the most stable site for the adsorption of O. Furthermore, the calculations also show that a C ↔ O exchange is exothermic on ZrC͑001͒, and the displaced C atoms bond to CZrZr sites. In the O / ZrC͑001͒ interface, the surface C atoms play a major role in determining the behavior of the system. In contrast, the adsorption of oxygen induces very minor changes in the C͑1s͒ spectrum of VC͑001͒. The O ↔ V interactions are stronger than the O ↔ Zr interactions, and O ↔ C interactions do not play a dominant role in the O / VC͑001͒ interface. In this system, C ↔ O exchange is endothermic. VC͑001͒ has a larger density of metal d states near the Fermi level than ZrC͑001͒, but the rate of oxidation of VC͑001͒ is slower. Therefore the O / ZrC͑001͒ and O / VC͑001͒ systems illustrate two different types of pathways for the oxidation of carbide surfaces.

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“…No visible diffraction lines attributable to rhodium crystalline phase of Rh-(x)L/Si catalysts appeared in XRD patterns, due to Rh has small particle diameter and the metal loading in these catalysts were was 1% wt of rhodium. On the contrary, non-stabilized Rh catalyst diffraction peaks, which had higher average particle diameter, showed up 2θ = 41.0º and 47.3º representing (111) and (200) planes of rhodium phase 37 . The most intense peak at 41.0 º was corroborated by electron diffraction analysis showing Rh (111).…”

Section: Catalysts Characterizationmentioning

confidence: 99%

CHIRAL Rh/SiO2 CATALYSTS FOR ENANTIOSELECTIVE HYDROGENATION REACTIONS: THE ROLE OF (S,S)-DIPAMP AS CHIRAL MODIFIER AND STABILIZER ON METALLIC NANOPARTICLES SYNTHESIS

Mella¹,

Ávila²,

SANCHEZ³

et al. 2013

J. Chil. Chem. Soc.

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Rhodium nanoparticles were successfully stabilized by the (S,S)-1,2-ethanediylbis [(2-ethoxyphenyl)phenylphosphine] ((S,S)-DIPAMP) deposited on SiO 2 prepared by a facile reduction and impregnation method. The chiral catalysts obtained were efficient for the enantioselective hydrogenation reactions of prochiral compounds. The catalysts synthesized from [Rh(μ-OMe)(COD)] 2 in the presence of different amounts of a ligand used as chiral stabilizer, showed good metal dispersion. As shown by TEM, the metal particle size ranged between 1 and 2 nm using stabilizer and 9.1 nm was achieved without chiral ligand. Other techniques were used to characterize the chiral catalysts such as X-ray diffraction (XRD), electron diffraction, thermogravimetric analysis (TGA) and N 2 adsorption-desorption isotherms.(S,S)-DIPAMP was used as the stabilizer of metal particles to prevent growing and agglomeration, and it also acts as chiral modifier inducing enantioselectivity in the asymmetric hydrogenation of 3,4-hexanodione (HD), ethyl pyruvate (EP), ketopantolactone (KP), and acetophenone (AP). Under specific conditions such as 25 °C, 40 bar of H 2 and substrate/Rh=100, 1%Rh-(S,S)-DIPAMP/SiO 2 chiral catalysts showed excellent catalytic performance with conversion and enantiomeric excess (ee) levels up to 99% and 54% respectively.

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Theory of bonding in transition-metal carbides and nitrides

Cited by 444 publications

References 24 publications

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

First-Principle Calculation Assisted Thermodynamic Assessment of the Pt-Pb System

Interaction of oxygen with ZrC(001) and VC(001): Photoemission and first-principles studies

CHIRAL Rh/SiO2 CATALYSTS FOR ENANTIOSELECTIVE HYDROGENATION REACTIONS: THE ROLE OF (S,S)-DIPAMP AS CHIRAL MODIFIER AND STABILIZER ON METALLIC NANOPARTICLES SYNTHESIS

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