Fe and Ni AB initio effective potentials for use in molecular calculations

Melius, Carl F.; Olafson, Barry D.; Goddard, William A.

doi:10.1016/0009-2614(74)80079-5

Cited by 149 publications

(74 citation statements)

References 13 publications

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“…16 This uses angular momentum projection operators (nonlocal ECP) to enforce the Pauli principle. [17][18][19][20] In the Jaguar program, this ECP uses the LACVP ** basis set for Pt, and all electrons for hydrogen and carbon were treated explicitly with the 6-31G ** basis set. 15,16 To test whether diffuse functions on the adsorbate might be necessary, we considered previously the case of oxygen on a Pt 28 cluster, where we found that adding diffuse functions increases the binding energy by only 0.015 eV.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Jacob

Goddard

2004

J. Phys. Chem. B

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We used the B3LYP flavor of density functional theory (DFT) to study the chemisorption of all CH x and C 2 H y intermediates on the Pt(111) surface. The surface was modeled with the 35 atom Pt 14.13.8 cluster, which was found to be reliable for describing all adsorption sites. We find that these hydrocarbons all bind covalently (σ-bonds) to the surface, in agreement with the studies by Kua and Goddard on small Pt clusters. In nearly every case the structure of the adsorbed hydrocarbon achieves a saturated configuration in which each C is almost tetrahedral with the missing H atoms replaced by covalent bonds to the surface Pt atoms. Thus, (Pt 3 )-CH prefers a µ 3 hollow site (fcc), (Pt 2 )CH 2 prefers a µ 2 bridge site, and PtCH 3 prefers µ 1 on-top sites. Vinyl leads to (Pt 2 )CH-CH 2 (Pt), which prefers a µ 3 hollow site (fcc). The only exceptions to this model are ethynyl (CCH), which binds as (Pt 2 )CdCH(Pt), retaining a CC π-bond while binding at a µ 3 hollow site (fcc), and HCCH, which binds as (Pt)HCdCH(Pt), retaining a π bond that coordinates to a third atom of a µ 3 hollow site (fcc) to form an off center structure. These structures are in good agreement with available experimental data. For all species we calculated heats of formation (∆H f ) to be used for considering various reaction pathways on Pt(111). For conditions of low coverage, the most strongly bound CH x species is methylidyne (CH, BE ) 146.61 kcal/mol), and ethylidyne (CCH 3 , BE ) 134.83 kcal/mol) among the C 2 H y molecules. We find that the net bond energy is nearly proportional to the number of C-Pt bonds (48.80 kcal/mol per bond) with the average bond energy decreasing slightly with the number of C ligands.

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Section: Theoretical Methodsmentioning

confidence: 99%

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Jacob

Goddard

2004

J. Phys. Chem. B

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“…For all functionals, we included the Grimme D3 London dispersion correction 12 . In our PBE and M06 calculations, we used the Pople 6-31G** basis set [13][14][15][16] for light atoms and the angular-momentum-projected 17,18 LANL2TZ effective core potential basis set 19,20 for vanadium atoms (denoted LACVP** within Jaguar). We performed B3LYP calculations using three different basis sets:…”

Section: Computational Detailsmentioning

confidence: 99%

Dual-Phase Mechanism for the Catalytic Conversion of n-Butane to Maleic Anhydride by the Vanadyl Pyrophosphate Heterogeneous Catalyst

2017

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Industrial production of maleic anhydride (MA) from n-butane relies on the vanadyl pyrophosphate (VPO) catalyst. Improving VPO's selectivity and activity could have enormous economic and environmental impact, but efforts have been impeded by uncertainties regarding the active phases and atomistic mechanism of the VPO catalyst. We report here a plausible 15 step mechanism taking n-butane to MA with energetics computed using hybrid density functional theory calculations on periodic models of the surface layers. We find that the P=O group on the X1 phase is solely responsible for butane activation. The P=O group is made active by the reduction of a nearby vanadium atom, a so-called reduction-coupled oxo-activation.However, we show that a catalyst consisting only of the X1 phase would not be selective due to several highly exothermic steps. Instead, we show that the more stable α 1 phase can catalyze the formation of MA after initial activation, thus proposing and validating a dual-phase mechanism that takes butane to MA. Our new mechanism inspires the development of a more selective VPO catalyst containing small X1 regions highly separated by α 1 surfaces.

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“…The Gaussian basis set consisted of an optimized double-ζ plus polarization Gaussian-type basis set contracted from calculations on the most stable unit cell of the pure elements. Angular-momentum-projected norm-conserving nonlocal effective core potentials [19][20][21][22] were used to replace the core electrons. Thus, the Pt atom is described with 16 explicit electrons (six 5p, one 6s, and nine 5d in the ground state).…”

Section: Computational Approachmentioning

confidence: 99%

Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties

et al. 2015

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a Electrochemical water-based energy cycles provide a most promising alternative to fossil-fuel sources of energy. However, current electrocatalysts are not adequate (high overpotential, lack of selectivity toward O 2 production, catalyst degradation). We propose here mechanistic guidelines for experimental examination of modified catalysts based on the dependence of kinetic rates on the solvent dielectric constant.To illustrate the procedure we consider the fcc(111) platinum surface and show that the individual steps for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) change systematically with the polarizability of the medium. Thus changing this environmental variable can be used to tune the rate determining steps and the barriers, providing a means for screening and validating new systems to optimize the rate determining steps for the ORR and OER reaction pathways.

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Fe and Ni AB initio effective potentials for use in molecular calculations

Cited by 149 publications

References 13 publications

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Dual-Phase Mechanism for the Catalytic Conversion of n-Butane to Maleic Anhydride by the Vanadyl Pyrophosphate Heterogeneous Catalyst

Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties

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Fe and Ni AB initio effective potentials for use in molecular calculations

Cited by 149 publications

References 13 publications

Chemisorption of (CHx and C2Hy) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Chemisorption of (CHx and C2Hy) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Dual-Phase Mechanism for the Catalytic Conversion of n-Butane to Maleic Anhydride by the Vanadyl Pyrophosphate Heterogeneous Catalyst

Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties

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Resources

About

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies

Chemisorption of (CH_x and C₂H_y) Hydrocarbons on Pt(111) Clusters and Surfaces from DFT Studies