Temperature dependence of the Raman frequencies and bandwidths close to phase transitions in ammonium halides

Yurtseven H.

JOURNAL OF MOLECULAR STRUCTURE, vol.595, pp.47-55, 2001 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 595
  • Publication Date: 2001
  • Doi Number: 10.1016/s0022-2860(01)00519-1
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.47-55
  • Istanbul Technical University Affiliated: No


In this study, we give the temperature dependence of our observed frequencies and bandwidths for the Raman optical modes in the ammonium halides close to the phase transitions of the first order (NH4 Br), tricritical (NH4Cl) and second order (NH4Cl). Using the predictions of an [sing pseudospin-phonon coupled model, which considers interactions between two spin and two phonons, our observed Raman data have been interpreted qualitatively. Our results show that an Ising model considered here can explain the observed behaviour of the Raman phonons near the phase transitions of the first order, tricritical and second order in the ammonium halides. (C) 2001 Elsevier Science B.V. All rights reserved.