Inelastic Neutron Spectra and the Vibrational Modes of the Hydrogen Layer in Alkali and Alkaline-Earth Hydroxides

Pelah, I.; Krebs, K.; Imry, Y.

doi:10.1063/1.1697043

Cited by 14 publications

(4 citation statements)

References 20 publications

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“…Inelastic neutron scattering studies of the low-energy (0−80 meV) vibrational modes of brucite at room temperature have been carried out by Safford et al and by Pelah et al . The peaks at 15.6, 38, 47.5, and 81.3 meV in Figure a agree well with the previous results albeit with small energy shifts due to temperature effects.…”

Section: Resultssupporting

confidence: 79%

“…The remaining E g libration and the lattice modes ranging from 30 to 100 meV are obscured by a cluster of strong combination bands over the 80−150 meV region. Combination modes of brucite, particularly in the vicinity of the stretch vibrations, have been studied extensively by many authors. ,,− Qualitatively, we may assign the peak centered at 509 meV as OH stretch + E u libration and the peak around 552 meV as OH stretch + 2E u librations. Similarly, the peak at ∼97 meV may be 2E u librations, and the side peaks at 115 and 132 meV may be 2E u + lattice modes.…”

Section: Resultsmentioning

confidence: 93%

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Low-Temperature Structure and Dynamics of Brucite

1997

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Structural refinements of time-of-flight neutron powder diffraction data for Mg(OD)2 and inelastic neutron scattering measurements for Mg(OH)2 demonstrate that the mechanism of thermal contraction is primarily the reduction of the octahedral thickness and secondarily the reduction of the interlayer thickness. The contraction of the octahedral layer thickness is 4 times as great as the contraction of the interlayer thickness over the temperature interval 300−15 K. The volume of brucite at 15 K is equivalent to that at 0.2 GPa, which should not be sufficient to observe the H-bonding between the octahedral layer that occurs at high pressure; however, the three-site split-atom model, in which the O−D direction makes an angle α with the 3-fold c axis, provides a better fit to the data for each temperature than the single-site model. The O−D distance from the single-site model is markedly shortened by the large atomic displacement parameter of the D atom, but if the O−D distance is corrected for “riding” motion, it lengthens roughly to the same values determined from the three-site split-atom model. The temperature dependence of the lattice parameters are given by a = 3.1435 + 2.911 × 10-5 T + 9.944 × 10-8 T 2 − 1.965 × 10-11 T 3 − 4.789 × 10-13 T 4, c = 4.7478 + 1.793 × 10-4 T + 4.496 × 10-7 T 2 + 3.910 × 10-10 T 3, V = 40.635 + 2.330 × 10-3 T + 5.592 × 10-6 T 2 + 1.748 × 10-9 T 3, for T in °C. The vibrational spectrum of hydrogen in Mg(OH)2 at 15 K obtained from inelastic scattering measurements shows a sharp OH stretch band at 461.8 meV, an Eu OH libration at 47.5 meV, and other broad features due to lattice vibrations and combination excitations. No evidence of enhanced hydrogen bonding was found at low temperatures.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 93%

Low-Temperature Structure and Dynamics of Brucite

1997

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“…2). Also remarkable is the similarity between the IR absorption spectra of brucite in this region, and the density of state of brucite as measured by neutron scattering (Pelah et al, 1965;Dawson et al, 1973). This is a strong argument favoring the fact that this spectral region is populated by -OH fundamental stretching and its combination with lattice vibration modes (Fig.…”

Section: The Nature Of the 306 Lm Featurementioning

confidence: 66%

Low-temperature reflectance spectra of brucite and the primitive surface of 1-Ceres?

Beck

Schmitt

Cloutis

et al. 2015

Icarus

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“…Da daftir die Wellenzahl k r 0 ist, kann dieser Schwingungszustand optisch nur dann angeregt werden, wenn akustische Schwingungen mit der gleichen Wellenzahl bereits angeregt sind. Das Neutronenstreuspektrum des Mg(OH)2 [3] zeigt, dab die obere Frequenzgrenzederakustischen Schwingungen bei 162 cm -1 liegt. Dies bedeutet, dab alle akustischen Schwingungen im Mg(OH)2-Gitter schon bei Zimmerteml~eratur thermisch angeregt sil~d, so dab also die optische Anregung der gegenphasigen OH-Knickschwingungen mSglich ist.…”

Section: Modell Fiir Schwingungskopplungunclassified

Zersetzungsmechanismus von Mg(OH)2 und Mg(OD)2

Nägerl

Freund

1970

Journal of Thermal Analysis

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The conditions have been studied under which the proton of an ionic OH-group can leave the electron cloud of the 0 3-ion to form a HeO molecule with a neighbouring OH-group. The condition of tunnelling is the presence of a free acceptor level of similar height in the neighbouring OH-group. If the two OH-groups are equivalent crystallographically, this condition is not fulfilled since the acceptor level lies higher than the donor level. Coupling with the opposite-phase OH bending vibrations leads to a broadening of the levels and finally to an overlap, which renders the tunnelling possible. The proton transfer starts at the surface as at any given temperature the amplitude of the effective OH bending vibrations is larger at the surface than inside the crystal. Abb. 1 zeigt einen Schnitt durch die Mg(OH)2-Struktur entlang (10i0). Es ist zu erwarten, dab die Tunnelfibertragung zwischen zwei benachbarten OH--Gruppen innerhalb der gleichen (0001)-Ebene erfolgt oder zwischen zwei "auf Lticke" gegentiberstehenden OH--Gruppen zweier benachbarter (0001)

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Inelastic Neutron Spectra and the Vibrational Modes of the Hydrogen Layer in Alkali and Alkaline-Earth Hydroxides

Cited by 14 publications

References 20 publications

Low-Temperature Structure and Dynamics of Brucite

Low-Temperature Structure and Dynamics of Brucite

Low-temperature reflectance spectra of brucite and the primitive surface of 1-Ceres?

Zersetzungsmechanismus von Mg(OH)2 und Mg(OD)2

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