Ferroelectric Phase Transition in Ammonium Hydrogen Bis (Chloroacetate). : IV. Heat Capacity of NH_4H(ClCH_2COO)_2 and ND_4D(ClCH_2COO)_2

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概要

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• Heat capacity of NH_4H(ClCH_2COO)_2 and ND_4D(ClCH_2COO)_2 was measured between 3 and 300K with an adiabatic calorimeter. It showed a lambda-shaped anomaly at 119.7 and 130.3K for the H and D salts, respectively, with the same entropy of transition of transition of about 1/2Rln 2. The isotope effects in chloroacetate anion were extracted by comparing the difference plot of normal heat capacity between two salts with that of NH_4Br and ND_4Br. A collective mode involving the short hydrogen bond in chloroacetate anion is indicated. The unusual behavior below 20K suggested that the D crystal is harder than the H crystal, and also led to the characteristic properties in these crystals. Two possible mechanisms of phase transition, continuous displacive type and order-disorder type, are examined by the observed heat capacity. Simple and modified order-disorder models are ruled out.

• 社団法人日本物理学会の論文
• 1976-05-15

著者

• CHIHARA Hideaki

  Faculty of Science, Osaka University

• Inaba Akira

  Faculty Of Science Osaka University

• Chihara Hideaki

  Faculty Of Science Osaka University

関連論文

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• Study of Ferroelectric Phase Transitions in the Rochelle Salt with the Pseudo-Spin-Lattice Coupled Mode Model
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• Ferroelectric Phase Transition in Ammonium Hydrogen Bis (Chloroacetate). : IV. Heat Capacity of NH_4H(ClCH_2COO)_2 and ND_4D(ClCH_2COO)_2
• Heat Capacity of Solid HCl near 120 K
• Note on the Theory of Nuclear Spin Relaxation Exact Formulae in the Weak Collision Limit

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