Vibrational states and optical transitions in hydrogen bonds

Johannsen, Peter

doi:10.1088/0953-8984/10/10/008

Cited by 21 publications

(27 citation statements)

References 37 publications

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“…The vibrational state of proton in one-dimensional potential deforming from a double to a single minimum shape has numerically been calculated using a generalized double Morse potential. 23 The essential features of the calculated results are illustrated in Fig. 7.…”

Section: Discussionmentioning

confidence: 99%

Raman study of phase transition and hydrogen bond symmetrization in solid DCl at high pressure

et al. 2000

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Phase transitions in solid DCl have been investigated by Raman spectral measurement up to 70 GPa at 298 K. The I-III phase transition accompanied by orientational ordering of the molecules took place at 19.0 Ϯ0.5 GPa, exactly the same pressure as observed for solid HCl. A further transition with hydrogen bond symmetrization ͑III-IV transition͒ was observed at about 56Ϯ2 GPa higher by 5 GPa than the symmetrization pressure of HCl previously determined. The bond symmetrization is realized when the midpoint barrier separating two potential minima along the hydrogen-bonding axis is depressed and smeared out quantum mechanically. The observed isotope effects on the symmetrization pressure are hence interpreted in terms of proton ͑deuteron͒ tunneling transfer in the hydrogen bonding potential, which gradually is deformed toward a single minimum shape with increasing pressures.

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Section: Discussionmentioning

confidence: 99%

Raman study of phase transition and hydrogen bond symmetrization in solid DCl at high pressure

et al. 2000

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“…A general description encompassing the previous physical systems is given by a simple one-dimensional model [23][24][25]31] of a quantum particle in a double well in the presence of a homogeneous electric field E, and focuses on the effect of the asymmetry induced by E [32]. It reads where x is the particle position along the O-O direction, P the pressure, and a, b, P 0 , and V 0 are fitting parameters adjusted to the mean potential energy calculated in pure ice [4].…”

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Quantum versus classical protons in pure and salty ice under pressure

et al. 2016

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It is generally accepted that nuclear quantum effects (NQEs) trigger the transition to the nonmolecular form of ice under increasing pressure. This picture is challenged in salty ice, where Raman scattering measurements up to 130 GPa of molecular ice VII containing NaCl or LiCl impurities show that the transition pressure to the symmetric phase ice X is shifted up by about 30 GPa, even at small salt concentrations. We address the question of how the inclusion of salt induces the drastic reduction of NQEs by selectively including NQEs in ab initio calculations of ice in the presence of distinct ionic impurities. We quantitatively show that this is mainly a consequence of the electric field generated by the ions. We propose a simple model that is able to capture the essence of this phenomenon, generalizing this picture to other charged defects and for any concentration. This result is potentially generalizable to most "dirty" ices in which the electric field due to the doping is much more significant than local lattice distortions. DOI: 10.1103/PhysRevB.93.024104 Ice under extreme conditions is present in many planets, both within our solar system [1] and beyond [2]. These ices are usually "dirty": Planetary real ices unavoidably contain impurities such as salt. In pure ice, nuclear quantum effects (NQEs) play a crucial role by drastically decreasing the VII-X phase transition pressure [3,4]. However, recent experiments question the role of NQEs in LiCl-doped ice [5]. Whether this is specific to LiCl ice and the mechanism by which the quantum behavior of the protons can be hindered is still an issue.At high pressure, the two molecular phases of ice, proton disordered ice VII and proton ordered ice VIII [6,7], transform to ice X, the only known atomic phase of ice. Below the transition, the oxygens form a body-centered-cubic structure, and the hydrogen bonds are characterized by a prototypical double-well proton transfer potential. As the atoms get closer under the effect of increasing pressure, the intrinsic quantum nature of the protons produces more evident effects and favors the onset of quantum tunneling. Upon further reducing the distance between oxygens, the proton potential degenerates into a single-well potential [8], giving rise to a symmetric hydrogen bond, where the hydrogen is located midway between two neighboring O atoms. By including NQEs, the transition pressure P t is drastically reduced from about 90 GPa as classically predicted [9] to approximately 60 GPa [10][11][12][13][14][15][16], that is, the pressure for which the zero-point energy equals the barrier height [3,4]. However, the effect of a perturbation on a prototype of structural quantum effects in crystals is not a priori trivial from a fundamental point of view.Recent studies [5] on LiCl-water solutions at different salt to water ratios pointed out that the properties of ice change drastically when LiCl salt is homogeneously included into ice VII and that the transition pressure to the phase X strongly depends on the presence of ionic...

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“…The transfer frequently occurs along an existing hydrogen bond bridge of the form O-H Á Á Á O, where the proton (H) occupies a double-well potential surface between two oxygen ions (O) [3]. The strong dependence of the tunneling rate on distance, i.e., barrier width, creates two interesting scenarios.…”

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Proton Tunneling: A Decay Channel of the O-H Stretch Mode inKTaO3

et al. 2009

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The vibrational lifetimes of the O-H and O-D stretch modes in the perovskite oxide KTaO3 are measured by pump-probe infrared spectroscopy. Both stretch modes are exceptionally long lived and exhibit a large "reverse" isotope effect, due to a phonon-assisted proton-tunneling process, which involves the O-Ta-O bending motion. The excited-state tunneling rate is found to be 7 orders of magnitude larger than from the ground state in the proton conducting oxide, BaCeO3 [Phys. Rev. B 60, R3713 (1999)].

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Vibrational states and optical transitions in hydrogen bonds

Cited by 21 publications

References 37 publications

Raman study of phase transition and hydrogen bond symmetrization in solid DCl at high pressure

Raman study of phase transition and hydrogen bond symmetrization in solid DCl at high pressure

Quantum versus classical protons in pure and salty ice under pressure

Proton Tunneling: A Decay Channel of the O-H Stretch Mode inKTaO3

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