Quantum-driven phase transition in ice described via an efficient Langevin approach

Bronstein, Yael; Depondt, Philippe; Finocchi, Fabio; Saitta, A. Marco

doi:10.1103/physrevb.89.214101

Cited by 67 publications

(78 citation statements)

References 39 publications

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“…The oxygen-oxygen T 2g vibrational mode, which is indicative of the cupritelike structure of phase X, clearly appears at 87 ± 5 GPa, similarly to what is observed in LiCl ice [5]. Thus, the presence of small quantities of salt impurities (here, 1 NaCl for 53 H 2 O), which is likely in natural ices, shifts P t by about 30 GPa, roughly the same pressure shift as observed when quantum effects are neglected in pure ice [3,4]. This observation confirms that the measured shift of P t in LiCl ice is actually a general effect of ionic impurities on the ice lattice.…”

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confidence: 59%

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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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“…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].…”

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Quantum versus classical protons in pure and salty ice under pressure

et al. 2016

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“…4 the main result of our experimental and computational study: The inclusion of ions pushes the ice VII to ice X to higher and higher pressures, and this occurs with a nearly exponential law, with a similar trend observed both from experiment and simulations. The shift of almost 35 GPa between the ab initio calculations and the experimental transition, defined by the appearance of the T 2g Raman mode, is likely due to quantum effects, and, in particular, to the fact that nuclei are approximated as classical particles in our ab initio molecular dynamics calculations, and are therefore unable to tunnel through the potential barrier (31). Moreover, our classical description of nuclei hinders a finer description of possible isotopic effects (32).…”

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confidence: 99%

“…Quantum effects play an essential role in the phenomenon of hydrogen bond centering; thus the description of ice VII and ice VIII transformation to the atomic ice X represents a stringent benchmark for theoretical calculations (27)(28)(29)(30)(31)(32)(33)(34)(35). First-principle calculations predict an intricate pretransitional behavior characterized by possible intermediate disordered ice X or VII phases (27)(28)(29)(30)35).…”

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“…In these two phases, the hydrogen bonds are characterized by a pronounced double-well proton transfer potential. Upon reducing the distance between donor and acceptor oxygens, the proton potential degenerates into a single-well potential (27)(28)(29)(30)(31), giving rise to a symmetric or centered hydrogen bond, where hydrogen atoms are located midway between two neighboring oxygen atoms. Infrared (IR), Raman, and X-ray measurements (5-10) have provided evidence for the transition in water from the molecular proton-disordered ice VII to an atomic phase with symmetric hydrogen bonds when the distance between acceptor and donor oxygen atoms decreases below 2.3 Å (at about 60 GPa).…”

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Effect of salt on the H-bond symmetrization in ice

Bove

Gáal

Raza

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The richness of the phase diagram of water reduces drastically at very high pressures where only two molecular phases, protondisordered ice VII and proton-ordered ice VIII, are known. Both phases transform to the centered hydrogen bond atomic phase ice X above about 60 GPa, i.e., at pressures experienced in the interior of large ice bodies in the universe, such as Saturn and Neptune, where nonmolecular ice is thought to be the most abundant phase of water. In this work, we investigate, by Raman spectroscopy up to megabar pressures and ab initio simulations, how the transformation of ice VII in ice X is affected by the presence of salt inclusions in the ice lattice. Considerable amounts of salt can be included in ice VII structure under pressure via rock-ice interaction at depth and processes occurring during planetary accretion. Our study reveals that the presence of salt hinders proton order and hydrogen bond symmetrization, and pushes ice VII to ice X transformation to higher and higher pressures as the concentration of salt is increased.salty ices | extreme conditions | ice bodies | H-bond symmetrization | proton quantum effects A ll models of the interior of ice bodies in the universe rely on our knowledge of the behavior of a few simple molecules under high pressure and temperature (1-22), water being the most intriguing of them, due to its abundance and its connection to life existence.New data delivered by various space missions, such as the Voyager, Galileo, and Cassini-Huygens missions, have greatly improved our understanding of the icy bodies within the solar system (23-25), and recent discoveries of extrasolar planets with significant water ice content have highlighted the importance of high-pressure H 2 O-rich phases in planetary physics beyond the solar system (26).Water displays an unusually rich pressure-temperature phase diagram, which mainly derives from the open geometry of the water molecule, which favors tetrahedral arrangements, and from the possibility of configurational disorder of the protons in the lattice. However, at high pressure (above about 2 GPa), the system experiences a large densification as a result of the interpenetration of low-pressure structures, and only two molecular phases are known, ice VIII and VII (3, 4). Ice VII is composed of two interpenetrating but not interconnected tetrahedral hydrogen-bonded networks of water molecules of normal cubic ice, Ic, with a body-centered-cubic (bcc) oxygen structure. The orientation of the water molecules is disordered, resulting in a paraelectric phase. In the antiferroelectric ice VIII phase, the water molecules and the associated dipole moments on the two sublattices possess long-range order and point in opposite directions, promoting a slight tetragonal distortion of the cubic unit cell along the staggered polarization (3, 4). In these two phases, the hydrogen bonds are characterized by a pronounced double-well proton transfer potential. Upon reducing the distance between donor and acceptor oxygens, the proton potential degenerate...

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The Fate of the Formic Acid Proton on the Anatase TiO₂(101) Surface

Fallacara,

Finocchi,

Cazzaniga

et al. 2024

Angewandte Chemie

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As a prototype adsorption reaction of gas Brønsted acid on oxides, we study the adsorption of formic acid on anatase. We perform infrared spectroscopy measurements of adsorbed HCOOH and HCOOD on TiO2 nanopowders, from 13 K up to room temperature in an ultra‐high vacuum chamber. We assign the IR signals via computed spectra from nuclear quantum dynamics simulations using our divide‐and‐conquer semiclassical ab initio molecular dynamics method. The acid proton forms an extraordinarily short and strong hydrogen bond with the surface oxygen. The strength of this hydrogen bond, that compares to H bonds in ice at high pressures, is at the root of a substantial redshift with respect to the typical free OH stretching frequency, which eludes its straightforward detection.

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Quantum-driven phase transition in ice described via an efficient Langevin approach

Cited by 67 publications

References 39 publications

Quantum versus classical protons in pure and salty ice under pressure

Quantum versus classical protons in pure and salty ice under pressure

Effect of salt on the H-bond symmetrization in ice

The Fate of the Formic Acid Proton on the Anatase TiO₂(101) Surface

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Quantum-driven phase transition in ice described via an efficient Langevin approach

Cited by 67 publications

References 39 publications

Quantum versus classical protons in pure and salty ice under pressure

Quantum versus classical protons in pure and salty ice under pressure

Effect of salt on the H-bond symmetrization in ice

The Fate of the Formic Acid Proton on the Anatase TiO2(101) Surface

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The Fate of the Formic Acid Proton on the Anatase TiO₂(101) Surface