The lambda-phase transitions in NH4Cl

Yurtseven H. H., Sherman W.

PHASE TRANSITIONS, vol.54, no.1, pp.1-13, 1995 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 54 Issue: 1
  • Publication Date: 1995
  • Doi Number: 10.1080/01411599508200400
  • Journal Name: PHASE TRANSITIONS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1-13
  • Keywords: lambda-phase transitions, mode Gruneisen parameter, Raman frequency, NH4Cl, MODE GRUNEISEN PARAMETERS, AMMONIUM HALIDES, NH4BR, HEAT, PRESSURE, SOLIDS, SYSTEM, POINT
  • Middle East Technical University Affiliated: No

Abstract

We show here the correlations between the volume changes and the vibrational frequencies of the disorder-induced Raman modes of NH4Cl near the lambda-phase transitions of first order (P=0), tricritical (P similar or equal to 1.6 kbar) and second order (P similar or equal to 2.8 kbar). We obtain the values of the mode Gruneisen parameter for each phonon across the lambda-phase transitions and use them to predict the Raman frequencies for the phonon modes studied as functions of temperature in the lambda-phase change regions.