Calculation of the specific heat for the first order, tricritical and second order phase transitions in NH4Cl

Yurtseven H. H., Kayisoglu D., Sherman W.

PHASE TRANSITIONS, vol.67, no.2, pp.399-412, 1998 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 67 Issue: 2
  • Publication Date: 1998
  • Doi Number: 10.1080/01411599808228749
  • Journal Name: PHASE TRANSITIONS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.399-412
  • Keywords: specific heat, phase transitions, Raman frequencies, NH4Cl, WEAKLY FIRST-ORDER, SPECTROSCOPIC MODIFICATIONS, PIPPARD RELATIONS, AMMONIUM HALIDES, SINGLE-CRYSTALS
  • Middle East Technical University Affiliated: No

Abstract

This work presents our calculation for the specific heat Cv under an Ising model that uses our Raman frequencies of the nu(7)TA (93 cm(-1)) and nu(5)TO (144 cm(-1)) modes for NH4Cl. The specific heat calculation has been performed for first-order (P = 0 kbar), tricritical (P = 1.6 kbar) and second-order (P = 2.8 kbar) phase transitions in the NH4Cl crystal. Our calculated Cv values are in good agreement with the experimentally observed Cp data from the literature for NH4Cl. This indicates that the NH4Cl crystal can be adequately described in the lattice region by means of the Ising model studied here.