On the Fluorine Molecule. Part I. The Pilot Calculation

Hijikata, Katsunori

doi:10.1063/1.1731567

Cited by 22 publications

(2 citation statements)

References 12 publications

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“…F 2 , the archetypical charge-shift bond, attains the high value of Q = 16.0. We do not include it in Figure ; if we did, its correlation energy would exceed 100% of the bond energy; that is, there is no bond in F 2 at the Hartree–Fock limit. − …”

Section: “Correlated” Bondsmentioning

confidence: 99%

Distinguishing Bonds

2016

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The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond.

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Section: “Correlated” Bondsmentioning

confidence: 99%

Distinguishing Bonds

2016

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“…1 shows PECs from HF and density functional theory (DFT). UHF does not predict a bound molecule, 21 while the restricted HF (RHF) curve is artificially bound with a minimum that is 5% too low compared to experiment. The DFT local spin-density approximation 23 (LSDA) and generalized gradient approximation 24 (GGA/PBE) yield dissociation energies which are too large.…”

Section: Spin Contamination Effects In the Dissociation Of The F mentioning

confidence: 99%

Eliminating spin contamination in auxiliary-field quantum Monte Carlo: Realistic potential energy curve of F2

Purwanto

Al-Saidi

Krakauer

et al. 2008

The Journal of Chemical Physics

106

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The use of an approximate reference state wave function mid R:Phi(r) in electronic many-body methods can break the spin symmetry of Born-Oppenheimer spin-independent Hamiltonians. This can result in significant errors, especially when bonds are stretched or broken. A simple spin-projection method is introduced for auxiliary-field quantum Monte Carlo (AFQMC) calculations, which yields spin-contamination-free results, even with a spin-contaminated mid R:Phi(r). The method is applied to the difficult F(2) molecule, which is unbound within unrestricted Hartree-Fock (UHF). With a UHF mid R:Phi(r), spin contamination causes large systematic errors and long equilibration times in AFQMC in the intermediate, bond-breaking region. The spin-projection method eliminates these problems and delivers an accurate potential energy curve from equilibrium to the dissociation limit using the UHF mid R:Phi(r). Realistic potential energy curves are obtained with a cc-pVQZ basis. The calculated spectroscopic constants are in excellent agreement with experiment.

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The Hartree-Fock dissociation of F2

Gordon

Truhlar

1987

Theoret. Chim. Acta

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On the Fluorine Molecule. Part I. The Pilot Calculation

Cited by 22 publications

References 12 publications

Distinguishing Bonds

Distinguishing Bonds

Eliminating spin contamination in auxiliary-field quantum Monte Carlo: Realistic potential energy curve of F2

The Hartree-Fock dissociation of F2

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