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Electron delocalization patterns in models of distorted mixed-valence cubanes
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10.1063/1.2960622
/content/aip/journal/jcp/129/5/10.1063/1.2960622
http://aip.metastore.ingenta.com/content/aip/journal/jcp/129/5/10.1063/1.2960622

Figures

Image of FIG. 1.
FIG. 1.

Schematic diagram of a tetranuclear “cubane” iron-sulfur cluster. The high-symmetry structure comprises interpenetrating tetrahedra of iron atoms and sulfur atoms. In this study, the effects of distortions along the axis are analyzed.

Image of FIG. 2.
FIG. 2.

Phase diagrams showing the delocalization pattern of an excess electron in a cluster with a closed-shell ion core for (a) compressed geometries and (b) elongated geometries. The quantity gives a measure of the relative magnitudes of electronic and vibronic coupling for tetranuclear clusters. corresponds to undistorted structures; corresponds to the limit of tetragonal compression (square planar structure); corresponds to the limit of tetragonal elongation (noninteracting dimers). The labels D, L, and P indicate full delocalization, localization, and pair delocalization of the excess electron, respectively.

Image of FIG. 3.
FIG. 3.

Contour diagram illustrating pair delocalization of an excess electron in a tetranuclear cluster with a closed-shell ion core. The cluster has an elongated structure, with parameters , , and (i.e., , ). The contours are plotted at intervals of 0.02 units, where is the symmetric ligand vibration frequency. The diagram is a section through the potential energy surface, plotted as a function of the dimensionless symmetrized ligand displacement coordinates and , with .

Image of FIG. 4.
FIG. 4.

Eigenvector coefficients ) as a function of the degree of metal center distortion for (a) compressed structures with and (b) elongated structures with . and correspond to the undistorted structure.

Image of FIG. 5.
FIG. 5.

Phase diagrams showing the delocalization pattern of an excess electron in an cluster with open-shell ion cores for (a) compressed geometries and (b) elongated geometries. The quantity gives a measure of the relative magnitudes of electronic and vibronic coupling for tetranuclear clusters. The magnitudes of the antiferromagnetic exchange interactions are and the vibronic coupling parameter is given by . corresponds to undistorted structures; corresponds to the limit of tetragonal compression (square planar structure); corresponds to the limit of tetragonal elongation (noninteracting dimers). The labels D, L, and P indicate full delocalization, localization, and pair delocalization of the excess electron, respectively.

Image of FIG. 6.
FIG. 6.

Eigenvector coefficients ) as a function of the degree of tetragonal elongation in the open-shell system, when , (i.e., ). corresponds to the undistorted structure. Small distortions from this pair-delocalized structure cause electron localization; further distortions cause a return to pair delocalization.

Image of FIG. 7.
FIG. 7.

Contour diagrams (details as in Fig. 3) illustrating pair delocalization of an excess electron in a tetranuclear cluster with an open-shell ion core. (a) Undistorted cluster with parameters ; ; and . (b) Elongated cluster with parameters , , (i.e., , ); , and .

Tables

Generic image for table
Table I.

Spin basis states used in the five-electron model. Label 1 represents the extra electron and the site of localization (, , , or ). is the local spin of the site containing the extra electron. Basis states having and are known as non-Hund states and Hund states, respectively. and are the intermediate spins of the remaining sites (, , , or ), where , , and are the spins of the electrons in core orbitals , , and . The total spin of the cluster can take the values .

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/content/aip/journal/jcp/129/5/10.1063/1.2960622
2008-08-06
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Electron delocalization patterns in models of distorted (D2d) mixed-valence cubanes
http://aip.metastore.ingenta.com/content/aip/journal/jcp/129/5/10.1063/1.2960622
10.1063/1.2960622
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