Wavefunctions for “4-electron, 3-centre” bonding units

Harcourt, Richard D.; Harcourt, Alison G.

doi:10.1039/f29747000743

Cited by 45 publications

(29 citation statements)

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“…4, but with the inclusion of configurations 1* to 4* , were prosecuted. 10 The principal results are collected in Table I and it is found that the general conclusions of the above analysis are upheld. Moreover, it is evident that 1 T 11 * 1 T 1 * 4 /A 11 * ( ϭ 1 T 14 * 1 T 4 * 4 /A 14 * ) has a calculated value of 0.041 18 eV with a 4 Å separation between the ethene monomers, and 0.020 20 eV for the 5 Å dimer.…”

Section: A Model Calculationsmentioning

confidence: 97%

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Scholes

Harcourt

1996

The Journal of Chemical Physics

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Structure of complex systems using electronic excitation transport: Theory, Monte Carlo simulations, and experiments on micelle solutions Electronic excitation transfer in clustered chromophore systems: Calculation of timeresolved observables for intercluster transfer J. Chem. Phys. 94, 5622 (1991); 10.1063/1.460498The psitype circular dichroism of large molecular aggregates. III. CalculationsThe theory established in J. Chem. Phys. 101, 10521 ͑1994͒, for electronic factors which promote interchromophore electronic energy transfer, exciton interactions and which provide the stabilization of excimers, is extended; first so as to include the possible contribution of doubly excited configurations. It is ascertained that there is a resultant effect upon the ͑interchromophore orbital overlap-dependent͒ through-configuration interaction, and a significant correction to the simple expression obtained previously for the Coulombic interaction. These CI effects are admitted to the general theory of the previous work and the cases of nonidentical, identical, and orthogonal donor and acceptor are discussed. Second, a description of superexchange effects is admitted to the theory. Two possible formalisms are developed and discussed.

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Section: A Model Calculationsmentioning

confidence: 97%

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Scholes

Harcourt

1996

The Journal of Chemical Physics

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“…For Lewis structure (6) we have now used three different formulations of the wavefunction for the four (20) Resonance between Lewis structures (4)-( 6) and ( 20) is e q ~i v a l e n t ~~' * * ~' -~~ to the utilization of the Linnett non-paired spatial orbital (NPSO) structure (17). The 'best' wavefunction for this structure involves two variational Resonance between the Lewis structures (4)-( 6) is equivalent '-399715p42, 43 to resonance between the increased-valence structures (18) and (19). Because Lewis structure (20) is unimportant, it is not surprising that the energies of (17) and ( 18…”

Section: Ir-electron Structurementioning

confidence: 99%

Ab initio valence bond calculations for the ground state of ozone

Harcourt¹,

Skrezenek²,

Wilson³

et al. 1986

J. Chem. Soc., Faraday Trans. 2

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The results of ab initio valence-bond calculations, with an STO-6G basis set, are reported for the ground state of ozone. Both Heitler-London and localized molecular-orbital procedures have been used to construct the wavefunctions for the a-bonds. Hybridization of the orbitals on each atom has been determined by energy considerations.In accord with previous results, the primary Lewis structure is calculated to be the spin-paired diradical structure ( 6 ) with two a-bonds, and a long, or formal, .rr-bond associated with the terminal atoms. However, the sum of weights for four Lewis structures (11)-( 14), which arise from polarization of either a-bond in (6), is calculated to exceed the weight for (6).Particular attention is given to the calculation of energies for 'increasedvalence' structures (1) and (2), which are constructed by spin-pairing the two unpaired electrons of ground-state O2 with those of a ground-state oxygen atom. If a two-centre molecular orbital is used to accommodate the two electrons of the 0-0 a-bond in each of these structures, then resonance between these structures is equivalent to resonance between numerous Lewis structures including (6) + (11)-( 14), when Heitler-London procedures are used to formulate the wavefunctions for all electron-pair bonds in the Lewis structures. The results of calculations which utilize this approach indicate that resonance between increased-valence structures provides the primary valence bond representation for the O3 ground state. Such structures are stabilized slightly by interaction with the Lewis structures that involve excited states for the 0 atom and the O2 molecule. The resulting energy for resonance between these four valence-bond structures lies at least 0.134 au below the STO-6G RHF-MO energy of -224.091 au.

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“…The "increased-valence'' structures for HF2-are (h) and (i) of Figure 2 [28]. They may be generated from the standard valence-bond structures 1 and 2 of Table V by (2)] to accommodate the bonding electrons, then resonance between "increased-valence'' structures (h) and (i) summarizes resonance between all of the valence-bond structures of Table V [15][16][17]. Indeed, if one uses a different bond parameter (k) for each of the three bonding electrons of the two "increased-valence" structures, the wave functions for the resonance between these two structures is equivalent to the valence-bond wave function for the resonance between the six valence-bond structures of Table V [17].…”

Section: Bifluoride Anion Hf2-mentioning

confidence: 99%

“…They may be generated from the standard valence-bond structures 1 and 2 of Table V by (2)] to accommodate the bonding electrons, then resonance between "increased-valence'' structures (h) and (i) summarizes resonance between all of the valence-bond structures of Table V [15][16][17]. Indeed, if one uses a different bond parameter (k) for each of the three bonding electrons of the two "increased-valence" structures, the wave functions for the resonance between these two structures is equivalent to the valence-bond wave function for the resonance between the six valence-bond structures of Table V [17]. Resonance between the standard valence-bond structures (j) and (k) of Figure 2, with doubly occupied bond orbitals to accommodate the two bonding electrons of these two structures, would summarize resonance between structures 1 and 2 (with Heitler-London wave functions for the electron-pair bonds) and 4-6 [15][16][17]181.…”

Section: Bifluoride Anion Hf2-mentioning

confidence: 99%

Valence‐bond studies of four‐electron three‐center bonding units. II. FNO, HNO, LiNO, LiON, and HF₂⁻

Harcourt

Roso

1979

Int J of Quantum Chemistry

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AbstractsFor each of HNO, FNO, LiNO, LiON and HFZ-, ab initio valence-bond wave functions are reported for the four-electron three-center bonding unit which involves one of the following sets of atomic orbitals: (a) NXg-bond ( X = H, For Li) and oxygen 2pn'; (b) LiO u-bond and nitrogen 2~7~' ; (c) hydrogen 1s and fluorine 2pu. Six S = 0 valence-bond structures pertain for this type of bonding unit. For HFZ-and FNO, the calculated bond-eigenfunction coefficients for some of these valencebond structures differ appreciably according to whether the Slater determinants include only the electrons of the four-electron three-center bonding unit, or all of the valence-shell + inner-shell electrons. For HNO, LiNO, and LiON, the all-electron and all valence-shell electron calculations generate similar sets of bond-eigenfunction coefficients. For each of the nitrosyl systems, the bond-eigenfunction coefficient with largest magnitude is calculated to be that for which zero atomic formal charges occur in the valence-bond structure. Qualitative valence-bond and "increasedvalence" descriptions of the bonding are presented.

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Wavefunctions for “4-electron, 3-centre” bonding units

Cited by 45 publications

References 0 publications

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Ab initio valence bond calculations for the ground state of ozone

Valence‐bond studies of four‐electron three‐center bonding units. II. FNO, HNO, LiNO, LiON, and HF₂⁻

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Wavefunctions for “4-electron, 3-centre” bonding units

Cited by 45 publications

References 0 publications

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Configuration interaction and the theory of electronic factors in energy transfer and molecular exciton interactions

Ab initio valence bond calculations for the ground state of ozone

Valence‐bond studies of four‐electron three‐center bonding units. II. FNO, HNO, LiNO, LiON, and HF2−

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Valence‐bond studies of four‐electron three‐center bonding units. II. FNO, HNO, LiNO, LiON, and HF₂⁻