Ab initio localized electron calculations on solvated electron structures

Clark, Timothy; Illing, Gerd

doi:10.1021/ja00238a006

Cited by 44 publications

(45 citation statements)

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“…-0.26) are much larger. The sign of the hyperfine constant on the oxygen atoms is positive, in agreement with previous results (3)(4)(5). It seems that positive hyperfine coupling constants, which are generally observed in solvated electrons, are caused by the spin polarization mechanism as already pointed out by Clark and Illing (5).…”

Section: Spirt Pop~~latiortsupporting

confidence: 91%

A model calculation on structures and excitation energies of the hydrated electron

Tachikawa¹,

Lund²,

Ogasawara³

1993

Can. J. Chem.

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HIROTO TACHIKAWA, ANDERS LUND, and MASAAKI OGASAWARA. Can. J. Chem. 71, 1 18 (1993). Model calculations were made on the hydrated electron by using the a 6 inirio MO method combined with the MR-SD-CI method and the coupled cluster theory. The models used in the calculations were water clusters denoted by [e-(HzO),,(HzO),,,], where n = 2,3,4, and 6 for the first solvation shell and m = 0-28 for the second and third solvation shells. In these model calculations, the interactions between the excess electron and the water molecules in the first solvation shell are explicitly calculated by rrb initio MO methods and the water inolecules in the second and third solvation shells were represented by the fractional charges obtained at the MP2/D95Ve:? level. The stabilization energies and the solvation radius r(e--O), in terms of the distance between the ccnter of the cavity and an oxygen atom of the surrounding water molecules, increased monotonically with the number of water n~olecules in the first solvation shell. On the other hand, the first excitation energy was not dependent on the number of water molecules in solvation shells, but constant, with thc value of ca. 2.0 cV. On the basis of the present calculations, we suggest that (1) the energetic stability of excess electrons depends on both short-range interaction and long-range interaction, (2) the first excitation energy is critically affected by only the short-range interactions, and the excitation is theoretically attributed to the 1-2p trailsition of the excess electron.

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Section: Spirt Pop~~latiortsupporting

confidence: 91%

A model calculation on structures and excitation energies of the hydrated electron

Tachikawa¹,

Lund²,

Ogasawara³

1993

Can. J. Chem.

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“…As discussed in detail in Ref. 24 an excess electron just off the H atoms will spin polarize the N-H bonds, and the spin density will have contributions from both, the unpaired electron and the spin polarized bonds. The similarity of spin density and orbital-based schemes suggests that for Li(NH 3 ) 4 the contributions from the bonds is small despite a strongly bound -and therefore close -excess electron.…”

Section: Ab Initio Resultsmentioning

confidence: 98%

Characterizing the excess electron of Li(NH3)4

Sommerfeld

Dreux

2012

The Journal of Chemical Physics

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Small lithium ammonia clusters are model systems for the dissociation of metals into solvated cations and electrons in ammonia. Metal-ammonia solutions display a complex behavior with increasing metal concentration including a phase change from a paramagnetic to a metallic diamagnetic phase, and small clusters should be useful models in the low concentration regime, where one may expect the ammoniated electron to show a behavior similar to that of the hydrated electron. Yet, even in the low concentration regime the nature of the ammoniated electron is still controversial with cavity models supported by optical and density measurements whereas localized radical models have been invoked to explain magnetic measurements. Small clusters can shed light on these open questions, and in particular the Li-NH(3) tetramer represents the smallest cluster with a complete solvation shell for the Li(+) cation. In view of the controversies about the character of the excess electron, the first question investigated is whether different theoretical characterizations of the "excess electron" lead to different conclusions about it. Only small differences are found between orbital-based and spin density-based and between self-consistent-field and coupled-cluster-based methods. Natural orbitals from equation-of-motion coupled-cluster calculations are then used to analyze the excess electron's distribution of Li(NH(3))(4) with particular emphasis on the portion of the excess electron's density that is closely associated with the N atoms. Three different comparisons show that only about 6% of the excess electron's density are closely associated with the atoms, with about 1% being closely associated with any N atom, and that the electron is best characterized as a Rydberg-like electron of the whole cluster. Finally, it is shown that in spite of the small amount of density close to the N atoms, the spin-density at the N nuclei is substantial, and that the magnetic observations can plausibly be explained within the cavity model.

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“…[55] There is in the literature a history of calculations on hydrated and ammoniated electrons in which an approach somewhat different from ours is followed (see Ref. [111] and references within). In these studies, a basis function (effectively a pseudoatom) is placed at the center of the cavity.…”

Section: Lithium-ammonia Solutionsmentioning

confidence: 99%

A Molecular Perspective on Lithium–Ammonia Solutions

2009

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A detailed molecular orbital (MO) analysis of the structure and electronic properties of the great variety of species in lithium-ammonia solutions is provided. In the odd-electron, doublet states we have considered: e-@(NH3)n (the solvated electron, likely to be a dynamic ensemble of molecules), the Li(NH3)4 monomer, and the [Li(NH3)4+.e-@(NH3)n] ion-pairs, the Li 2s electron enters a diffuse orbital built up largely from the lowest unoccupied MOs of the ammonia molecules. The singly occupied MOs are bonding between the hydrogen atoms; we call this stabilizing interaction H-->H bonding. In e-@(NH3)n the odd electron is not located in the center of the cavities formed by the ammonia molecules. Possible species with two or more weakly interacting electrons also exhibit H-->H bonding. For these, we find that the singlet (S=0) states are slightly lower in energy than those with unpaired (S=1, 2...) spins. TD-DFT calculations on various ion-pairs show that the three most intense electronic excitations arise from the transition between the SOMO (of s pseudosymmetry) into the lowest lying p-like levels. The optical absorption spectra are relatively metal-independent, and account for the absorption tail which extends into the visible. This is the source of Sir Humphry Davy's "fine blue colour" first observed just over 200 years ago.

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Ab initio localized electron calculations on solvated electron structures

Cited by 44 publications

References 0 publications

A model calculation on structures and excitation energies of the hydrated electron

A model calculation on structures and excitation energies of the hydrated electron

Characterizing the excess electron of Li(NH3)4

A Molecular Perspective on Lithium–Ammonia Solutions

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