Journal ArticleDOI
Theory of the Transition in KH2PO4
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In this paper, the theory of spontaneous polarization along the axis of the crystal, resulting in a well-known transition, similar to Rochelle salt, with polarization below the Curie point was worked out.Abstract:
Potassium dihydrogen phosphate contains phosphate groups connected by hydrogen bonds. Different possible arrangements of the hydrogens result effectively in different orientations of the (H2PO4)— dipoles. Since these have the lowest energy when pointing along the axis of the crystal, there is a tendency toward spontaneous polarization along this axis, resulting in the well‐known transition, similar to Rochelle salt, with polarization below the Curie point. The theory of this transition is worked out, using statistical methods to count the number of arrangements of hydrogens consistent with each total polarization of the crystal, and deriving the free energy. It is found that the theory predicts a phase change of the first order, with sudden transition from the polarized state at low temperature to the unpolarized state at high temperature, rather than the lambda‐point transition or phase change of the second order which is observed. However, the observed transition is confined to a very narrow temperature range compared to that predicted, for instance, by the Weiss theory, so that it seems as if it might be merely a broadened transition of the first order. It is suggested that the broadening may result from the irregular shifts of transition temperatures of individual domains in the crystal on account of stresses resulting from the large piezoelectric effect and the resulting deformation of the crystal below the transition point. The susceptibility above the Curie point comes out by the theory to be 4.33 times as great as it should according to the Weiss theory, a result which seems to be in general agreement with experiment. The entropy change in the transition is given by the theory as 0.69 unit, somewhat smaller than the observed value of about 0.8 unit. No explanation is suggested for this discrepancy.read more
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Dielectric Properties of Ice I
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Hydrogen-bonded donor–acceptor compounds for organic ferroelectric materials
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Theory of the Phase Transition in the Quasi-One-Dimensional Hydrogen-Bonded Ferroelectric Crystal PbHPO 4
A. V. de Carvalho,S. R. Salinas +1 more
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High pressure phase transitions and hydrogen‐bond symmetry in ice polymorphs
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References
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Journal ArticleDOI
The Structure and Entropy of Ice and of Other Crystals with Some Randomness of Atomic Arrangement
Journal ArticleDOI
Eine neue seignette-elektrische Substanz
G. Busch,P. Scherrer +1 more
TL;DR: Wasps social and solitary, problems of ins t inct and intelligence, development and behavior, and notes on how to deal with these problems and more.
Journal ArticleDOI
Properties of Rochelle Salt
TL;DR: In a qualitative way, the anomalous properties of Rochelle salt can be explained on the basis of four different theories: ($a$) on the dipole theory, ($b$) by assuming polymorphic transitions at the Curie points, ($c) by postulating an anomalous piezoelectric effect, and ($d$) with an interaction theory which assumes that the structure and the fundamental properties of the crystal have no unusual characteristics as mentioned in this paper.