The potential energy curve of the proton and the dissociation energy of the OH− ion in Mg(OH)2

Martens, R. L.; Freund, Friedemann

doi:10.1002/pssa.2210370112

Cited by 35 publications

(14 citation statements)

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“…The effect of the formation of H bonding does not seem to affect the compression behavior nor the Mg-O sublattice, because present data does not show any discontinuity in either unit-cell change or the atomic displacement at about 5 GPa. Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 9/29/15 9:59 AM Martens and Freund (1976) suggested that the shortening of the interlayer O ... O distance enhances proton transfer from donors to acceptors of O atoms. Indeed, Shinoda and Aikawa (1998) explained the pressure dependence of IR absorbency by the increasing proportion of proton transfer between interlayers with pressure.…”

Section: Resultsmentioning

confidence: 99%

Compression mechanism of brucite: An investigation by structural refinement under pressure

Nagai

Hattori

Yamanaka

2000

American Mineralogist

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Synchrotron X-ray powder diffraction study of brucite, Mg(OH) 2 , was carried out in a diamond anvil cell with an imaging plate detector from 0.6 to 18.0 GPa at room temperature using the angular-dispersive technique on beamline BL-18C at the Photon Factory, KEK, Japan. Using Rietveld analysis, unit-cell parameters as well as atomic positions of the O atoms in brucite have been successfully refined, taking into account the effects of preferred orientation. Variation of the c/a ratio with pressure indicates that the compression mechanism changes around 10 GPa, above which the compression behavior is isotropic. Based on the changes of the refined atomic positions of the O atoms with pressure, we conclude that the shortening of the interlayer distance controls compression below 10 GPa, whereas above this pressure compression of the oxygen sublattice is the dominant mechanism. Results of the structural refinements also suggest that the MgO 6 octahedral regularity initially approaches a regular configuration with pressure, which then remains unchanged above 10 GPa.

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Section: Resultsmentioning

confidence: 99%

Compression mechanism of brucite: An investigation by structural refinement under pressure

Nagai

Hattori

Yamanaka

2000

American Mineralogist

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“…02 through equations (1) and (2) for the IR mode only. Actually the attribution of the frequencies at 7157 (brucite) and 7084 cm À1 (portlandite) to the IR overtone, rather than to a combination of the IR and Raman fundamental frequencies as proposed by Mitra [35] and other authors [36,37], leaves some marginal doubt about the proposed ! e x e values.…”

Section: Comparison With Experimentsmentioning

confidence: 97%

Quantum mechanical calculation of the OH vibrational frequency in crystalline solids

Tosoni

Pascale²,

Ugliengo

et al. 2005

Molecular Physics

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The OH vibrational frequency of four crystalline compounds ranging from ionic (brucite, Mg(OH) 2 , and portlandite, Ca(OH) 2 ) to semi-covalent (edingtonite, as representative of free surface OH groups in silica, and acid chabazite, as representative of acid zeolites) has been investigated at quantum mechanical level with the CRYSTAL program using the B3LYP hybrid functional. The OH vibration is calculated in two ways: (i) in the harmonic approximation, by diagonalizing the fully coupled dynamical matrix to yield the harmonic frequency ! h . (ii) at the anharmonic level, by decoupling the OH stretching mode from the bulk phonons and by numerically solving the one-dimensional Schro¨dinger equation associated with the OH potential energy to yield the fundamental ! 01 and the first overtone ! 02 frequencies. The harmonic and anharmonic frequencies differ by more than 150 cm À1 . In the cases where direct comparison is possible (brucite, portlandite and edingtonite), the experimental and calculated frequencies differ by less than 10 cm À1 ; the calculated anharmonicity constant, ! e x e ¼ (2! 01 À ! 02 )/2, is systematically smaller than the experimental value by about 10 cm À1 . The effect of the computational parameters on the computed frequencies is explored, with particular attention to the grid used for the construction of the DFT exchange and correlation contribution to the Hamiltonian and the accuracy in the geometry optimisation.

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“…Graham (1981) proposed that the transport of hydrogen in epidote and zoisite is preceded by hydrolysis of the Si-O and Al-O bonds, followed by a proton transfer by a slower diffusion of (OH) or H 2 O. OH or H 2 O species are unlikely to diffuse in hydrous minerals, especially at low temperature, because of the donors OH and the acceptors O′ in the neighboring layer), and simultaneously increases the strength of the bonding between H and O atoms in the next layer. The potential barrier between proton sites in adjacent OH − groups is proportional to the O … O′ distance (Martens and Freund 1976). Therefore the proton migration through Equation 11 is enhanced by compression.…”

Section: Pressure Effect On the Proton Diffusivity In Brucitementioning

confidence: 98%

“…The previous studies focused on whether brucite forms pressure-induced hydrogen bonds between hydroxyls on a brucite layer and oxygen atoms on the adjacent layer or not (Sherman 1991;D'Arco et al 1993;Parise et al 1994;Catti et al 1995). The study of Martens and Freund (1976) suggested that the potential barrier for proton transfer between two neighboring hydrogen atoms in brucite would be reduced by compression. The infrared (IR) study of Shinoda and Aikawa (1998) and theoretical calibrations by Mookherjee and Stixrude (2006) have both shown that the proton transfer across the interlayer might be strongly * E-mail: gxzhuan@misasa.okayama-u.ac.jp enhanced under pressure, that is, the pressure has a positive effect on the mobility of proton.…”

Section: Introductionmentioning

confidence: 96%

H-D interdiffusion in brucite at pressures up to 15 GPa

Guo

Yoshino

Okuchi

et al. 2013

American Mineralogist

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Proton diffusion in brucite was investigated by conducting hydrogen-deuterium (H-D) exchange experiments using multi-anvil high-pressure apparatuses at pressures from 3 to 15 GPa and temperatures in the range of 750-1050 K. The diffusion couple was composed of a natural proton-dominated brucite single crystal surrounded by synthesized D-doped brucite polycrystals. Micro-Raman spectroscopy was used to determine the diffusion profiles of the samples. The D/H diffusion profile across the boundary between single crystal and polycrystalline D-doped brucite showed an asymmetric pattern characterized by faster diffusion in aggregates. The D/H interdiffusion rate determined from the analysis of the single crystal side indicates that the interdiffusion rate increases with increasing H/D ratio. The H-D interdiffusion rate in the direction perpendicular to the c-axis is about 0.5 orders of magnitude higher than that in the direction parallel to the c-axis. At 3 GPa, the H-D interdiffusion coefficients [D(m 2 /s)] along and perpendicular to the c-axis of brucite at compositions of C O no D rm = 0.2 in the single-crystal region were determined to be 3.30(±1.77) ×10 −11 exp[-48.2(±5.8) (kJ/mol)/ RT] and 1.43(±1.33) ×10 −9 exp[-67.5(±23.2) (kJ/mol)/RT], respectively. The H-D interdiffusion rate perpendicular to and along the c-axis increased about one order of magnitude by compression from 3 to 10 GPa, but the pressure enhancement became weaker above 10 GPa. From 10 to 15 GPa, there is almost no pressure dependence of proton diffusion for both directions. As pressure increases up to 10 GPa, enhancement of the proton migration is strongly correlated with the activation of the atomic interaction and decrease of O … O′ distance induced by compression. The positive pressure effect on the proton diffusion in brucite suggests that proton diffusion in higher-pressure hydrous phase becomes faster because of the shorter O … O′ distance.

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The potential energy curve of the proton and the dissociation energy of the OH− ion in Mg(OH)2

Cited by 35 publications

References 9 publications

Compression mechanism of brucite: An investigation by structural refinement under pressure

Compression mechanism of brucite: An investigation by structural refinement under pressure

Quantum mechanical calculation of the OH vibrational frequency in crystalline solids

H-D interdiffusion in brucite at pressures up to 15 GPa

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