Vibrational studies and phase transitions in Co(ClO4)2·6H2O and Mn(ClO4)2·6H2O

Patel, Monal; Patel, S. N.; Khandelwal, D. P.; Bist, H. D.

doi:10.1016/0009-2614(83)80311-x

Cited by 17 publications

(13 citation statements)

References 15 publications

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“…Such various types of H 2 O molecules were seen for example in Ref. [22] for CoHP (cobalt perchlorate hexahydrate) and MnHP (manganese perchlorate hexahydrate) which are isomorphous with NiHP [23]. This seems to be in correspondence with the conclusion from Ref.…”

Section: Assignment Of Some Peaks Of Gðxþ Functionsupporting

confidence: 84%

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Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Rachwalska

Natkaniec

2004

Physica B: Condensed Matter

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Section: Assignment Of Some Peaks Of Gðxþ Functionsupporting

confidence: 84%

“…We have adopted this because for MnHP there are three bands in the Raman spectrum at 360 cm À1 , 288 cm À1 , 214 cm À1 . They were assigned to u 1 ðA 1g Þ; u 3 ðF 2g Þ and u 2 ðE g Þ; respectively, of the metal-oxygen vibration in the octahedral aquocomplex [22].…”

Section: Assignment Of Some Peaks Of Gðxþ Functionmentioning

confidence: 99%

Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Rachwalska

Natkaniec

2004

Physica B: Condensed Matter

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“…38 III transition is a symmetry reducing deformation of the water ligand octahedron ͑MgHP; 32 NiHP; 30 ZnHP; 31 MnHP͒. 41 This changes the H 2 O-ClO 4 distances and may lead to the formation of hydrogen bonds. Further support comes from the observed increase in activation energy, which is in the range of weak hydrogen bonds.…”

Section: The Hindering Potential In Phase IIImentioning

confidence: 99%

Hydrogen dynamics in [Me(H2O)6](ClO4)2 with Me=Mg, Mn, Fe, Ni, and Zn investigated with quasielastic neutron scattering

Nöldeke

Asmussen

Press

et al. 2000

The Journal of Chemical Physics

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The hydrogen dynamics in the metalhexahydrateperchlorates with Mg, Mn, Fe, Ni, and Zn as metal ions has been investigated with quasielastic neutron scattering. The water molecules perform 180°-flip motions on a picosecond time scale through a series of solid–solid phase transitions. In the highest temperature phase I and the subsequent phase II, rotational barriers of typically Ea=50 meV are found. These values are surprisingly small in view of the low symmetry of H2O molecules. The I → II phase transition has only very small effects on the hydrogen dynamics. At the transition into phase III an increase of the rotational barriers to typically Ea=250 meV is found. This is interpreted as the formation of weak hydrogen bonds. In phase I 180°-flip motions provide a complete description of the observed data. In phases II and III an extension of the dynamical model toward a stronger localization of hydrogen is required. A preference is given to a mechanism leading to a temporary blockade of the flip motions. In phase III of the Fe compound, the existence of crystallographically different sites for water molecules is inferred.

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“…130 K (in the DSC experiment registered at T C3 = 126 K) and the second one occurring at ca. 160 K (not observed by us in the DSC experiment but registered by NMR [5] and IR, RS spectroscopy [7]). Some very small differences between diffraction patterns at 170 and 225 K can be also observed and can be related to orientational disorder of H 2 0 groups above 250 K which is very clearly seen in the IINS spectra (see Fig.…”

Section: Resultsmentioning

confidence: 73%

“…Phase transitions in these compounds have been detected by many methods, however there exists considerable disagreement concerning the transition temperatures and even the number of phases [3], especially for the compounds with M = Mn, Fe, and Co. For [Mn(H 2 0) 6 ](C10 4 ) 2 the following transition temperatures were detected: 323,247 and 135 K by DSC and adiabatic calorimetry [3,4], 160 and 89 K by NMR [5], 120 K by magnetic susceptibility [6], and 341, 248 and 161 K by IR and RS [7],…”

Section: Introductionmentioning

confidence: 99%

Phase Transitions and Water Dynamics of [Mn(H₂O)₆](ClO₄ )₂ Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

Mikuli¹,

Migdał-Mikuli²,

Natkaniec³

et al. 2000

Zeitschrift Für Naturforschung A

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DSC measurements performed at 95 -290 K have shown that [Mn(H 2 0) 6 ](C10 4 ) 2 possesses, besides a high-temperature phase, existing above 323 K, four low-temperature solid phases. The inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) patterns registered at 20 -290 K have supported the DSC results and provided evidence that the investigated substance possesses even more than five solid phases. The IINS spectra have shown that in the room-temperature phase, water molecules perform fast stochastic reorientation at the picosecond scale. The orientational disorder characteristic for the room-temperature phase can be easily overcooled and frozen. Even by relatively slow cooling at ca. 40 K/hour a metastable, orientational (protonic) glass phase is formed below ca. 160 K. Below ca. 100 K, a structural phase transition was observed by the NPD, however the IINS spectra indicate existence of the pure ordered low-temperature phase only after annealing the sample for a few hours at 100 K. On heating, a structural phase transition takes place at ca. 120 K, and at ca. 225 K water molecules begin fast reorientation.

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Vibrational studies and phase transitions in Co(ClO4)2·6H2O and Mn(ClO4)2·6H2O

Cited by 17 publications

References 15 publications

Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Hydrogen dynamics in [Me(H2O)6](ClO4)2 with Me=Mg, Mn, Fe, Ni, and Zn investigated with quasielastic neutron scattering

Phase Transitions and Water Dynamics of [Mn(H₂O)₆](ClO₄ )₂ Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

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Vibrational studies and phase transitions in Co(ClO4)2·6H2O and Mn(ClO4)2·6H2O

Cited by 17 publications

References 15 publications

Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Low-frequency vibrations and molecular motions of H2O molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 studied with neutron scattering methods

Hydrogen dynamics in [Me(H2O)6](ClO4)2 with Me=Mg, Mn, Fe, Ni, and Zn investigated with quasielastic neutron scattering

Phase Transitions and Water Dynamics of [Mn(H2O)6](ClO4 )2 Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

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Phase Transitions and Water Dynamics of [Mn(H₂O)₆](ClO₄ )₂ Studied by Differential Scanning Calorimetry and Neutron Scattering Methods