ESR Identification of Slater Configurations and of Exchange of the (AsO4)4− Radical in Irradiated Ferroelectric KH2AsO4 and KD2AsO4 and Antiferroelectric NH4H2AsO4 and ND4D2AsO4

Lamotte, B.; Gaillard, Jacques; Constantinescu, O.

doi:10.1063/1.1678761

Cited by 73 publications

(12 citation statements)

References 23 publications

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“…From physical point of view, this means the following phase transition mechanisms at negativeε: a significant tunnelling destroys the ground state ferroelectric configuration created by the short range interactions, whereas the long range interactions establish an antiferroelectric ordering. However, the existence of this mechanisms can be verified only with new experimental studies; in particular, the results of [45] should be confirmed. Therefore, at present it is difficult to unambiguously choose between the sets 2 and 3 for NH 4 H 2 AsO 4 .…”

Section: Numerical Analysis and Comparison With Experimental Datamentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamics and Dielectric Properties of the Nh_4h_2po_4 Type Antiferroelectrics

Levitskii¹,

Lisnii²,

Baran³

2002

Condens. Matter Phys.

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Within the framework of the proton model we study thermodynamic and static dielectric properties of the ADP type antiferroelectrics with taking into account the tunnelling effects of protons on hydrogen bonds. In the fourparticle cluster approximation for the short-range interactions and in the mean field approximation for the long-range interactions we calculate the free energy, entropy, and components of static dielectric susceptibility of the crystals. We also get the system of equations for the sublattice proton order parameter and an equation for the phase transition temperature. We find the values of the theory parameters for the NH 4 H 2 PO 4 and NH 4 H 2 AsO 4 crystals and get a good agreement between the theoretical results and the corresponding experimental data for the temperature dependences of the spontaneous sublattice polarization, proton specific heat, longitudinal and transverse static dielectric permittivities of the crystals.

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Section: Numerical Analysis and Comparison With Experimental Datamentioning

confidence: 99%

“…In [45] using the EPR it was established that in the disordered phase of the NH 4 H 2 AsO 4 crystal the number of up-down configurations of the H 2 AsO 4 radicals is larger than that of the lateral configurations. It means that the configurational energyε in NH 4 H 2 AsO 4 can be negative.…”

Section: Numerical Analysis and Comparison With Experimental Datamentioning

confidence: 99%

Thermodynamics and Dielectric Properties of the Nh_4h_2po_4 Type Antiferroelectrics

Levitskii¹,

Lisnii²,

Baran³

2002

Condens. Matter Phys.

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“…A need to revisit the developed theory of the phase transitions in antiferroelectric orthophosphates was indicated by the results of EPR studies. [55]. They showed that in the disordered phase in NH 4 H 2 AsO 4 there exist more upper/lower configurations of H 2 AsO 4 groups than lateral ones.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics and dynamical properties of the KH_{2}PO_{4} type ferroelectric compounds. A unified model

Levitskii¹,

Zachek²,

Vdovych³

et al. 2009

Condens. Matter Phys.

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Within the framework of the proposed unified proton ordering model for the ferroelectric compounds of the KH 2 PO 4 family, in the four-particle cluster approximation for the short-range interactions and mean field approximation for the long-range interactions, we calculate thermodynamic and longitudinal dynamic characteristics of the KD 2 PO 4 type ferroelectrics and ND 4 D 2 PO 4 type antiferroelectrics. Calculations for partially deuterated K(H 1−x Dx) 2 PO 4 type ferroelectrics and N(H 1−x Dx) 4 (H 1−x Dx) 2 PO 4 type antiferroelectrics are performed within the mean crystal approximation. It is shown that at the proper choice of the theory parameters, a good quantitative description of experimental data for the KH 2 PO 4 family crystals is obtained.

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“…Most of the phosphate groups in NHaH2PO 4 and KHzPO 4 are POz(OH)2 groups. The PO3(OH ) and PO(OH)3 groups discussed by Takagi (1948) are transient excited states representing a small part of the population of phosphate groups in ADP or KDP (see the work on RT-NH4HzAsO4 by Lamotte, Gaillard & Constantinescu, 1972). The geometrical shape of ordered POz(OH)2 groups is known from several precise crystal structure determinations" ferroelectric KH2PO 4 (Bacon & Pease, 1955), N2H6(H2PO4) 2 (Liminga, 1966) and NzHs(HzPO4) (Liminga, 1965).…”

Section: Disorder In Room-temperature Adp and Kdpmentioning

confidence: 99%

Reconstruction of local atomic environments in the disordered hydrogen-bonded crystal structures of paraelectric ammonium dihydrogen phosphate and potassium dihydrogen phosphate

Baur¹

1973

Acta Crystallogr Sect B

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In crystal structures in which one equivalent position is randomly occupied by different atomic species of different sizes the adjoining atoms must exhibit positional disorder. A special case is the statistical presence or absence of hydrogen atoms as observed in NH4H2PO4 (ADP) and KH2PO4 (KDP), where the bond lengths in the phosphate group will vary locally depending on whether it is a P-O or a P-O-H [P-O(h)] bond. The ideal shape of an individual PO2(OH)2 group is predicted on the basis of the extended electrostatic valence rule and the O-P-O on P-O dependence in orthophosphate groups: P-O 1.501 A, P-O(h) 1.573 A, O(h)-P-O(h) 105"8 °, O(h)-P-O 109-2 ° and O-P-O 113.9 ~. This calculated PO2(OH)2 group is fitted into unit cells of the same dimensions but lower symmetry than those of the paraelectric 1742d structures of ADP and KDP. These hypothetical local environments in C~, 9 (/-centered) and P21212~ are compatible with the observed averaged structure deduced from X-ray diffraction data for ADP. The hydrogen-atom positions as calculated for the least electrostatic energy in the local environments agree with their positions as determined from neutron-diffraction data. The local environments display interatomic distances which differ from the distances in the averaged structure individually as well as in their average values. Therefore, the bond lengths derived from the refinement of averaged disordered structures should be viewed with extreme caution. The distance between the averaged atomic positions can be different from the average of the individual distances. The situation resembles the case of the effects which thermal motion has on the estimation of bond distances. In these instances a valid correction is only possible if we have information on the nature of the thermal motion or on the type of disorder in the crystal structure. Such information is generally not available.

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ESR Identification of Slater Configurations and of Exchange of the (AsO4)4− Radical in Irradiated Ferroelectric KH2AsO4 and KD2AsO4 and Antiferroelectric NH4H2AsO4 and ND4D2AsO4

Cited by 73 publications

References 23 publications

Thermodynamics and Dielectric Properties of the Nh_4h_2po_4 Type Antiferroelectrics

Thermodynamics and Dielectric Properties of the Nh_4h_2po_4 Type Antiferroelectrics

Thermodynamics and dynamical properties of the KH_{2}PO_{4} type ferroelectric compounds. A unified model

Reconstruction of local atomic environments in the disordered hydrogen-bonded crystal structures of paraelectric ammonium dihydrogen phosphate and potassium dihydrogen phosphate

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