Ab Initio Investigation of the Temporary Anion States of Perfluoroethane

Falcetta, M. F.; Choi, Yoojin; Jordan, Kenneth D.

doi:10.1021/jp001782l

Cited by 35 publications

(53 citation statements)

References 25 publications

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“…The orbital energies are an accidental product of the basis set. The study of the resonances is an interesting topic in itself, we refer to the extensive review on alkenes and alkynes by Jordan and Burrow, 58 and to computational work by Jordan and coworkers 59,60 and Cheng and Chen 61 on the determination of these resonances. If one uses the typical quantum chemistry method of finite basis sets (instead of scattering calculations with e.g.…”

Section: Orbital Energies Of Virtual Orbitalsmentioning

confidence: 99%

The Kohn–Sham gap, the fundamental gap and the optical gap: the physical meaning of occupied and virtual Kohn–Sham orbital energies

Baerends¹,

Gritsenko²,

Meer³

2013

Phys. Chem. Chem. Phys.

400

387

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A number of consequences of the presence of the exchange-correlation hole potential in the Kohn-Sham potential are elucidated. One consequence is that the HOMO-LUMO orbital energy difference in the KS-DFT model (the KS gap) is not "underestimated" or even "wrong", but that it is physically expected to be an approximation to the excitation energy if electrons and holes are close, and numerically proves to be so rather accurately. It is physically not an approximation to the difference between ionization energy and electron affinity I-A (fundamental gap or chemical hardness) and also numerically differs considerably from this quantity. The KS virtual orbitals do not possess the notorious diffuseness of the Hartree-Fock virtual orbitals, they often describe excited states much more closely as simple orbital transitions. The Hartree-Fock model does yield an approximation to I-A as the HOMO-LUMO orbital energy difference (in Koopmans' frozen orbital approximation), if the anion is bound, which is often not the case. We stress the spurious nature of HF LUMOs if the orbital energy is positive. One may prefer Hartree-Fock, or mix Hartree-Fock and (approximate) KS operators to obtain a HOMO-LUMO gap as a Koopmans' approximation to I-A (in cases where A exists). That is a different one-electron model, which exists in its own right. But it is not an "improvement" of the KS model, it necessarily deteriorates the (approximate) excitation energy property of the KS gap in molecules, and deteriorates the good shape of the KS virtual orbitals.

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Section: Orbital Energies Of Virtual Orbitalsmentioning

confidence: 99%

The Kohn–Sham gap, the fundamental gap and the optical gap: the physical meaning of occupied and virtual Kohn–Sham orbital energies

Baerends¹,

Gritsenko²,

Meer³

2013

Phys. Chem. Chem. Phys.

400

387

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show abstract

“…This difference is attributed to the positively charged carbon backbone, in analogy to the low-lying anion state in Si 2 H 6 , which is also a consequence of the positively charged Si atoms. 105 A theoretical investigation of perfluoroethane by Falcetta et al 106 reveals that C 2 F 2 6 possesses a bound 2 B u (C 2h ) state with an adiabatic electron affinity of 1.57 eV and a vertical detachment energy of 1.23 eV. This state emerges from the Jahn-Teller distortion of the 2 E u negative ion state.…”

Section: Some Reactions and Unusual Anion States In The Gas Phasementioning

confidence: 99%

5 Gas-phase stabilities of small anions

Kalcher

2001

Annu. Rep. Prog. Chem., Sect. C

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“…13,15,[26][27][28] In addition, the working equation must be closely correlated to the physical properties associated with hard (soft) species. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] A negative electron affinity indicates that the ''outermost'' electron is described by a resonance embedded in the continuous spectrum of the neutral species. A survey of the physical and chemical properties of the hardness was recently performed by one of the authors.…”

Section: Introductionmentioning

confidence: 99%

Should negative electron affinities be used for evaluating the chemical hardness?

Cárdenas

Ayers

Proft

et al. 2011

Phys. Chem. Chem. Phys.

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Despite recent advances in computing negative electron affinities using density-functional theory, it is an open issue as to whether it is appropriate to use negative electron affinities, instead of zero electron affinity, to compute the chemical hardness of atoms and molecules with metastable anions. We seek to answer this question using the accepted empirical rules linking the chemical hardness to the atomic size and the polarizability; we also propose a new correlation with the C6 London dispersion coefficient. For chemical reactivity in the gas phase, it seems to make no difference whether negative, or zero, electron affinities are used for systems with metastable anions. For reactions in solution the evidence that is presently available is insufficient to establish a preference. In addressing this issue, we noted that electron affinity data from which atomic chemical hardness values are computed are out of date; an update to Pearson's classic 1988 table [Inorg. Chem., 1988, 27, 734-740] is thus provided.

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Ab Initio Investigation of the Temporary Anion States of Perfluoroethane

Cited by 35 publications

References 25 publications

The Kohn–Sham gap, the fundamental gap and the optical gap: the physical meaning of occupied and virtual Kohn–Sham orbital energies

The Kohn–Sham gap, the fundamental gap and the optical gap: the physical meaning of occupied and virtual Kohn–Sham orbital energies

5 Gas-phase stabilities of small anions

Should negative electron affinities be used for evaluating the chemical hardness?

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