Theory of the order parameter in NaNO2 in the molecular field approximation

Bonilla, I.R., Holz, A. and Rutt, H.N. (1974) Theory of the order parameter in NaNO2 in the molecular field approximation. Physica Status Solidi, 63, (1), 297-305.


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A static theory of the order-disorder, ferro-paraelectric phase transition in NaNO2 is developed. The Coulomb energy of the system is calculated in the point charge approximation. The model takes the relative displacement ?°(T) of the Na+ ions from their symmetrical position as a function of temperature into account; and the strong correlation of the Na+ ion position with the dipole orientation of the neighboring NO2? ion. The short range force potential acting on the Na+ ion is fitted by means of ?°(0) which can be taken from experiment. The long-range order parameter ? is calculated in the molecular field approximation. A first order phase transition is obtained for which the critical values Tc and ?c are calculated as a function of the permanent electric dipole moment of NO2? and ?°(0). Only qualitative agreement with experimental results is obtained. The Made-lung constant of the lattice is obtained as ? = 1.93.

Item Type: Article
Divisions : Faculty of Physical Sciences and Engineering > Electronics and Computer Science
ePrint ID: 258458
Accepted Date and Publication Date:
May 1974Published
Date Deposited: 05 Nov 2003
Last Modified: 31 Mar 2016 13:59
Further Information:Google Scholar

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