Ultrasonic frequency shifts close to the first order and tricritical phase transitions in NH4Cl

Yurtseven H. H., Tari O., Bas M.

JOURNAL OF MOLECULAR STRUCTURE, vol.598, pp.109-116, 2001 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 598
  • Publication Date: 2001
  • Doi Number: 10.1016/s0022-2860(01)00628-7
  • Journal Name: JOURNAL OF MOLECULAR STRUCTURE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.109-116
  • Keywords: Pippard relations, ultrasonic frequencies, NH4Cl, PIPPARD RELATIONS, AMMONIUM HALIDES, SPECTROSCOPIC MODIFICATIONS, SINGLE-CRYSTALS, RAMAN-SPECTRA, MODE
  • Middle East Technical University Affiliated: No

Abstract

This study examines our spectroscopic modifications of the Pippard relations using the ultrasonic frequencies of the q[110] and q[1 (1) over bar0] modes for the first order phase transition in NH4Cl. We also examine our relations using the ultrasonic frequencies of the q[110] mode for the tricritical phase transition in this crystal. From our plots of the specific heat C-p as a function of the frequency shifts (1/nu)(partial derivative nu/partial derivativeT)(p), we obtain that our spectroscopically modified Pippard relation considered here is satisfied for those phonon modes studied close to the first order and tricritical phase transitions in NH4Cl. (C) 2001 Elsevier Science B.V. All rights reserved.