<i>Ab Initio</i> Effective Potentials for Use in Molecular Calculations

Kahn, Luis R.; Goddard, William A.

doi:10.1063/1.1677597

Cited by 140 publications

(55 citation statements)

References 34 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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“…We used all-electron basis sets of triple-ζ quality for Na, S, and K, 47,48 but for Cu, Ga, Se, Cd, and In, we used the SBKJC Relativistic effective core potentials (based on angular momentum projection operators 49,50 ) and the associated basis sets. 51 Thus we treat explicitly just the outer 19 electrons for Cu, 21 for Ga, 6 for Se, 20 for Cd, and 21 for In.…”

Section: Computational Detailsmentioning

confidence: 99%

Predicted roles of defects on band offsets and energetics at CIGS (Cu(In,Ga)Se2/CdS) solar cell interfaces and implications for improving performance

Xiao

Goddard

2014

The Journal of Chemical Physics

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The laboratory performance of CIGS (Cu(In,Ga)Se 2 ) based solar cells (20.8% efficiency) makes them promising candidate photovoltaic devices. However, there remains little understanding of how defects at the CIGS/CdS interface affect the band offsets and interfacial energies, and hence the performance of manufactured devices. To determine these relationships, we use density functional theory with the B3PW91 hybrid functional that we validate to provide very accurate descriptions of the band gaps and band offsets. This confirms the weak dependence of band offsets on surface orientation observed experimentally. We predict that the conduction band offset (CBO) of perfect CuInSe 2 /CdS interface is large, 0.79 eV, which would dramatically degrade performance. Moreover we show that band gap widening induced by Ga adjusts only the valence band offset, and we find that Cd impurities do not significantly affect the CBO. Thus we show that Cu vacancies at the interface play the key role in enabling the tunability of CBO. We predict that Na further improves the CBO through electrostatically elevating the valence levels to decrease the CBO, explaining the observed essential role of Na for high performance. Moreover we find that K leads to a dramatic decrease in the CBO to 0.05 eV, much better than Na. We suggest that the efficiency of CIGS devices might be improved substantially by tuning the ratio of Na to K, with the improved phase stability of Na balancing phase instability from K. All these defects reduce interfacial stability slightly, but not significantly.

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“…(This means that the "core" may consist of any chosen combination of filled angular-momentum manifolds of atomic orbitals.) This local" moder' potential may be used to replace the core-valence interaction to obtain (24) where F' contains only valence-valence electron interactions. In this equation, the sum of the pseudopotential and model potential may be usefully referred to as the" effective potential.…”

Section: =1mentioning

confidence: 99%

“…(24) and this form of V mod, particularly in atoms heavier than those of the first row, we have calculated the orbital energies of the valence s and p orbitals (i. e., the outermost pair of angular-momentum manifolds) of the four halogen atoms F through 1. The results are given in …”

Section: =1mentioning

confidence: 99%

On pseudopotential and effective-potential SCF theory and its application to compounds of heavy elements

Ewig

Wazer

1975

The Journal of Chemical Physics

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An effectivepotential approach to stationary scattering theory for longrange potentials A formulation of pseudopotential and effective-potential theory is developed within the framework of the Hartree-Fock formalism. It is shown that one-electron pseudopotentials may be used for many-valenceelectron atoms and molecules. An SCF computational procedure (the NOCOR method) is described that requires a minimal amount of parameterization. Sample calculations are performed on the four halogen atoms and ten dihalogen molecules. These results indicate that the "frozen-core" approximation is quite accurate at least through the fourth row of the Periodic Table. 1 N N H=L(-~.li -Z/r;)+ ZLLr;-}.If the above separability conditions are satisfied, the total energy derived from this Hamiltonian may be separated into core and valence terms,where Ee depends only on the nuclear charge and the core orbitals, which we will assume are known functions, and

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Ab Initio Effective Potentials for Use in Molecular Calculations

Cited by 140 publications

References 34 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

Predicted roles of defects on band offsets and energetics at CIGS (Cu(In,Ga)Se2/CdS) solar cell interfaces and implications for improving performance

On pseudopotential and effective-potential SCF theory and its application to compounds of heavy elements

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Ab Initio Effective Potentials for Use in Molecular Calculations

Cited by 140 publications

References 34 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

Predicted roles of defects on band offsets and energetics at CIGS (Cu(In,Ga)Se2/CdS) solar cell interfaces and implications for improving performance

On pseudopotential and effective-potential SCF theory and its application to compounds of heavy elements

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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