Calculation of the specific heat close to the first-order and second-order phase transitions in ammonium halides

Yurtseven H. H., Yanik A.

JOURNAL OF MOLECULAR STRUCTURE, vol.553, pp.267-279, 2000 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 553
  • Publication Date: 2000
  • Doi Number: 10.1016/s0022-2860(00)00570-6
  • Journal Name: JOURNAL OF MOLECULAR STRUCTURE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.267-279
  • Keywords: Raman, phase transitions, ammonium halides, WEAKLY FIRST-ORDER, SINGLE-CRYSTALS, NH4CL, NH4BR, SYSTEM
  • Middle East Technical University Affiliated: No

Abstract

This study presents our calculation of the specific heat C-v1 under the prediction of an Ising model. For this calculation we used our observed Raman frequencies for the l'5LO (177 cm(-1)) mode of NH4Br, the v(5)TO (144 cm(-1)) and v(1)TA (93 cm(-1)) modes of NH4Cl close to the first-order phase transitions (P = 0). We also calculate the specific heat Cvi using our observed Raman frequencies for the v(1)TA (93 cm(-1)) mode of NH4Cl close to the second-order phase transition (P = 2.8 kbar) in this crystalline system.