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Analysis of the Raman frequencies of a lattice mode in NH4Cl close to the tricritical and second order phase transitions
Date
2006-4
Author
Yurtseven, Hasan Hamit
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We analyze here our observed Raman frequencies of the nu(5) (174 cm(-1)) mode in NH4Cl close to its tricritical (P = 1.6 kbar) and the second order (P = 2.8 kbar) phase transitions. The critical behavior of the frequency shifts 1/nu (partial derivative nu/partial derivative T)(P) for this optical mode is described by a power-law with the critical exponent a. Our values of a = 0.01 (T < T-C) and a = 0.11 (T > T-C) for P = 1.6 kbar in NH4Cl are close to the values of 0.066 (=1/16) below T-C and 0.125 (=1/8) above T-C for the specific heat C-P due to a three-dimensional Ising model. Our value of a = 0. 18 (T < T-C) for P = 2.8 kbar in NH4Cl is also close to the Ising value (1/16), whereas our value of a = 0.64 (T > T-C) is far from the Ising value (1/8), which can be reasonably compared with those obtained by previous workers, for the thermal expansivity alpha(P) and the specific heat C-P in this crystalline system.
Subject Keywords
Raman frequencies
,
Lattice mode
,
NH4Cl
URI
https://hdl.handle.net/11511/28611
Journal
Chemical Physics
DOI
https://doi.org/10.1016/j.chemphys.2005.10.015
Collections
Department of Physics, Article
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H. H. Yurtseven, “Analysis of the Raman frequencies of a lattice mode in NH4Cl close to the tricritical and second order phase transitions,”
Chemical Physics
, pp. 574–578, 2006, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/28611.