Phase diagram of thiourea at atmospheric pressure under electric field : a theoretical analysisReport as inadecuate




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Abstract : The phase diagram of thiourea in the E, T plane at atmospheric pressure P0 is discussed in terms of a single harmonic approximation for the modulated phase. We use a Landau-Ginzburg approach of the type used to discuss Lifshitz points ; in this approach the temperature dependence of the square of the modulation wave vector is accounted for by the temperature dependence of the negative exchange stiffness constant. This theory allows qualitative as well as semi-quantitative understanding of the phase diagram, which is shown to exhibit a tricritical point in the close neighbourhood of an isolated critical point.

Keywords : critical points electric field effects ferroelectric materials ferroelectric transitions organic compounds phase diagrams thiourea atmospheric pressure electric field phase diagram single harmonic approximation modulated phase Landau Ginzburg approach temperature dependence modulation wave vector negative exchange stiffness constant tricritical point isolated critical point





Author: P. Lederer C.M. Chaves

Source: https://hal.archives-ouvertes.fr/



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