A coupled-mode model relating Raman line shape to high ionic conductivity

A. Nitzan; M. A. Ratner; D. F. Shriver

doi:10.1063/1.439516

A coupled-mode model relating Raman line shape to high ionic conductivity

A. Nitzan^*, M. A. Ratner, D. F. Shriver

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

Abstract

A phenomenological model, based on the generalized Langevin equation scheme first developed by Bruesch, Zeller, and co-workers, is employed to calculate the Raman band shapes for metal-halogen stretching modes in ionic conductors of the Ag₂HgI₄ class. The observed strong broadening of the Hg-I₄ stretch mode near 122 cm^-1 is explained as arising from coupling to the mobile ion diffusive mode. Below the β→α phase transition, the Ag-I mode is oscillatory, and the coupling effect is negligible on either Ag-I or Hg-I. In the conducting phase, the long time diffusive character of the Ag-I motion results in a strong effective damping of the Hg-I motion, leading to the observed broadening. The coupling effects are strong only when one of the two modes is indeed diffusive, thus explaining the apparent value of the Raman linewidth as a screening device for possible new ionic conductor crystals.

Original language	English (US)
Pages (from-to)	3320-3326
Number of pages	7
Journal	The Journal of Chemical Physics
Volume	72
Issue number	5
DOIs	https://doi.org/10.1063/1.439516
State	Published - 1979

ASJC Scopus subject areas

General Physics and Astronomy
Physical and Theoretical Chemistry

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title = "A coupled-mode model relating Raman line shape to high ionic conductivity",

abstract = "A phenomenological model, based on the generalized Langevin equation scheme first developed by Bruesch, Zeller, and co-workers, is employed to calculate the Raman band shapes for metal-halogen stretching modes in ionic conductors of the Ag2HgI4 class. The observed strong broadening of the Hg-I4 stretch mode near 122 cm-1 is explained as arising from coupling to the mobile ion diffusive mode. Below the β→α phase transition, the Ag-I mode is oscillatory, and the coupling effect is negligible on either Ag-I or Hg-I. In the conducting phase, the long time diffusive character of the Ag-I motion results in a strong effective damping of the Hg-I motion, leading to the observed broadening. The coupling effects are strong only when one of the two modes is indeed diffusive, thus explaining the apparent value of the Raman linewidth as a screening device for possible new ionic conductor crystals.",

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T1 - A coupled-mode model relating Raman line shape to high ionic conductivity

AU - Nitzan, A.

AU - Ratner, M. A.

AU - Shriver, D. F.

PY - 1979

Y1 - 1979

N2 - A phenomenological model, based on the generalized Langevin equation scheme first developed by Bruesch, Zeller, and co-workers, is employed to calculate the Raman band shapes for metal-halogen stretching modes in ionic conductors of the Ag2HgI4 class. The observed strong broadening of the Hg-I4 stretch mode near 122 cm-1 is explained as arising from coupling to the mobile ion diffusive mode. Below the β→α phase transition, the Ag-I mode is oscillatory, and the coupling effect is negligible on either Ag-I or Hg-I. In the conducting phase, the long time diffusive character of the Ag-I motion results in a strong effective damping of the Hg-I motion, leading to the observed broadening. The coupling effects are strong only when one of the two modes is indeed diffusive, thus explaining the apparent value of the Raman linewidth as a screening device for possible new ionic conductor crystals.

AB - A phenomenological model, based on the generalized Langevin equation scheme first developed by Bruesch, Zeller, and co-workers, is employed to calculate the Raman band shapes for metal-halogen stretching modes in ionic conductors of the Ag2HgI4 class. The observed strong broadening of the Hg-I4 stretch mode near 122 cm-1 is explained as arising from coupling to the mobile ion diffusive mode. Below the β→α phase transition, the Ag-I mode is oscillatory, and the coupling effect is negligible on either Ag-I or Hg-I. In the conducting phase, the long time diffusive character of the Ag-I motion results in a strong effective damping of the Hg-I motion, leading to the observed broadening. The coupling effects are strong only when one of the two modes is indeed diffusive, thus explaining the apparent value of the Raman linewidth as a screening device for possible new ionic conductor crystals.

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A coupled-mode model relating Raman line shape to high ionic conductivity

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