Critical behaviour of the specific heat calculated using the Raman frequencies of the lattice and internal modes near the lambda-phase transition in NH4Br

Date

2007-05-27

Author

Sen, S.
Yurtseven, Hasan Hamit

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We calculate here the specific heat of NH4Br using our Raman frequency shifts for the lattice mode Of nu(7) TA (56 cm(-1)) and the internal mode Of nu(2) (1684 cm(-1)) near its lambda-phase transition (T-lambda = 234 K, P = 0). By analyzing our Raman frequency shifts, values of alpha = 0. 19 (T < T-lambda, and T > T-lambda) for the lattice mode, and alpha = 0.45 (T < T-lambda) and alpha = 0.57 (T > T-lambda) for the internal mode, are used as the values of the critical exponent for the specific heat to predict its critical behaviour based on an Ising model near the lambda-phase transition in NH4Br. The specific heat which we calculate here using our frequencies of both Raman modes, agrees well with the observed specific heat Cp near the lambda-phase transition in NH4Br. Some discrepancy occurring in the specific heat above T-lambda, due to the lattice mode is explained within the framework of an Ising pseudospin-phonon coupled model for NH4Br.

Subject Keywords

Inorganic Chemistry, Organic Chemistry, Analytical Chemistry, Spectroscopy

URI

https://hdl.handle.net/11511/36022

Journal

JOURNAL OF MOLECULAR STRUCTURE

DOI

https://doi.org/10.1016/j.molstruc.2006.10.063

Collections

Department of Physics, Article

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Citation Formats

S. Sen and H. H. Yurtseven, “Critical behaviour of the specific heat calculated using the Raman frequencies of the lattice and internal modes near the lambda-phase transition in NH4Br,” JOURNAL OF MOLECULAR STRUCTURE, pp. 561–566, 2007, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/36022.