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Three-parameter correlation functions for the calculation of thermal conductivity of gases, liquids, and refrigerants over wide temperature-pressure ranges
Yousef Ghayeb, Bijan Najafi, Elham Daneshmand, Gholamabbas Parsafar

We calculated the specific heat CVI close to the λ-phase transition in NH4Br on the basis of predictions of the Ising model. We have used our observed Raman frequencies of the ν5 (134 cm-1) lattice mode to extract the critical exponent for the specific heat. The CVI values calculated by us with this exponent value agree with the measured CP data reported in the literature. This agreement is particularly good above Tλ. This indicates that the observed behaviour of NH4Br can be satisfactorily explained close to the λ-phase transition in this crystal.

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