Mixed Valence Compounds: Temperature variation of the intervalence absorption band of hexachloroantimonate(III, V) ions in a crystal lattice

Kosmas Prassides, Peter Day

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

The bandshape of the intervalence absorption of SbC16 3- and SbCl6 -, has been measured from 300 to 4 K in a crystal of (CH3NH3) 2SbxSn1-x, C16 in order to study the variation of the zeroth, first and second moments. At all temperatures the bandshape is Gaussian, as required by the vibronic model of Piepho, Krausz and Schatz (P.K.S.) in the weak-interaction limit. From the temperature dependence of the second moment, we estimate the electronphonon coupling constant (and hence the displacement in vibrational coordinate from the ground state to the intervalence charge-transfer state), together with the effective phonon frequency coupled to the transition. The latter is very close to the mean of the ground-state totally symmetric Sb-Cl strtching modes of SbCl6 3- and SbCl6 - and the displacement in vibrational coordinate is also about half the difference between the Sb-Cl crystallographic bond lengths in the two complex ions. To explain the temperature dependence of the zeroth and first moments anharmonicity must be involved. A simple model for the variation of intervalence excitation energy with interionic distance, combined with an isotropic model of the thermal lattice expansion, gives a quantitative account of the change in first moment with temperature and a qualitative description of the change in zeroth moment.

Original languageEnglish
Title of host publicationMolecules into Materials
Subtitle of host publicationCase Studies in Materials Chemistry-Mixed Valency, Magnetism and Super Conductivity
PublisherWorld Scientific Publishing Co.
Pages389-399
Number of pages11
ISBN (Electronic)9789812706836
ISBN (Print)9812700382, 9789812700384
DOIs
Publication statusPublished - 2007 Jan 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Engineering(all)
  • Materials Science(all)
  • Physics and Astronomy(all)

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