Analysis of the Raman frequencies close to the λ-phase transition in NH4Cl

✍ Scribed by H. Yurtseven; T.U. Tuzer

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 137 KB
• Volume: 834-836
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2006.10.062

✦ Synopsis

This study gives our analysis of the Raman frequencies for the lattice modes of m 5 TO(174 cm À1 ), m 5 TO(144 cm À1 ) and m 7 TA(93 cm À1 ), and an internal mode of m 2 (1708 cm À1 ) as functions of temperature in NH 4 Cl close to its k-phase transition (T k = 241.2 K, P = 0). This analysis is performed using a power-law formula with the critical exponent b for the order parameter according to the soft mode-hard mode coupling model.

Our b value is very close to zero for all the modes studied in NH 4 Cl close to its k-phase transition. This indicates that the soft modehard mode coupling theory predicts a logarithmic divergence of the Raman frequencies of those modes considered here, as the temperature increases toward the k transition temperature T k in NH 4 Cl.