Journal ArticleDOI
Proton magnetic resonance study of molecular motion in (NH4)2HAsO4 and (NH4)2HPO4
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In this paper, temperature dependences of the second moments of the proton magnetic resonance absorption spectra and spin-lattice relaxation times are measured in (NH4)2HAsO4 and (NH 4)2HPO4.Abstract:
The temperature dependences of the second moments of the proton magnetic resonance absorption spectra and spin-lattice relaxation times are measured in (NH4)2HAsO4 and (NH4)2HPO4. Characteristic T1 minima and proton line width transitions are found demonstrating the existence of two chemically different NH4 groups in the unit cell. The anomalous increase in the As75 NQR frequency with increasing temperature in (NH4)2HAsO4 is explained as a result of thermally induced “acid” proton fluctuations in the HAsO4 groups.
In (NH4)2HAsO4 and (NH4)2HPO4 werden die Temperaturabhangigkeiten der zweiten Momente der magnetischen Protonenresonanzabsorptionsspektren und Spin—Gitter-Relaxationszeiten gemessen. Charakteristische T1-Minima und Ubergange der Protonenlinienbreiten werden gefunden und zeigen die Existenz von zwei chemisch verschiedenen NH4-Gruppen in der Einheitszelle an. Der anomale Anstieg in der As75-NQR-Frequenz mit steigender Temperatur in (NH4)2HAsO4 wird als Ergebnis thermisch induzierter „azider” Protonenfluktuationen in den HAsO4-Gruppen interpretiert.read more
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Study of internal motions and phase transitions in (NH4)2ZnCl4 and [(N(CH3)4)]2 ZnCl4 by proton magnetic resonance and relaxation
TL;DR: In this article, the authors measured the spin-lattice relaxation time and second moment in polycrystalline ammonium tetrachlorozincate (ATC-Zn) and tetramethyl ammonium TetrACHlorozinic (TMATC)-Zn as a function of temperature, covering the phase transitions.
Journal ArticleDOI
75As NQR study of some hydrogen-bonded monohydrogen arsenates
TL;DR: The 75As Zeeman perturbed NQR spectra of (NH4)2HAsO4 as well as the 75As NQRs of Na2.5H2O and Na2HASO4 were investigated in this paper, where it was shown that the NH4 group changes the structure of the ordered phase from a ferroelectric to an antiferroelectric one.
Journal ArticleDOI
High pressure NQR study of some monohydrogen arsenates with positive temperature coefficients
TL;DR: In this article, the NQR frequency of 75 As nuclei in mono-and dihydrogen arsenates under high hydrostatic pressure has been studied and it has been shown that totally different molecular mechanisms are responsible for the temperature and pressure dependence of the frequency in arsenates with positive and negative ∆v/∆T values.
References
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Journal ArticleDOI
Ferroelectricity in lead monohydrogen phosphate, PbHPO4, and the deuterated form, PbDPO4
TL;DR: In this paper, the deuterated form of PbHPO4 and PbDPO4 were found to be ferroelectric at room temperature with space group Pc.