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

Research output: Contribution to journalArticle

16 Citations (Scopus)

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 languageEnglish (US)
Pages (from-to)3320-3326
Number of pages7
JournalThe Journal of Chemical Physics
Volume72
Issue number5
StatePublished - Dec 1 1979

Fingerprint

Halogens
Ionic conductivity
Linewidth
coupled modes
ion currents
Stretching
line shape
Screening
Damping
Phase transitions
Metals
Ions
Crystals
conductors
halogens
screening
damping
conduction
metals
crystals

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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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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A coupled-mode model relating Raman line shape to high ionic conductivity. / Nitzan, A.; Ratner, M. A.; Shriver, D. F.

In: The Journal of Chemical Physics, Vol. 72, No. 5, 01.12.1979, p. 3320-3326.

Research output: Contribution to journalArticle

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