Proton disorder and the dielectric constant of type II clathrate hydrates

Rick, Steven W.; Freeman, David L.

doi:10.1063/1.3294563

Cited by 19 publications

(12 citation statements)

References 59 publications

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“…In particular, the static permittivity follows the typical 1/ T trend, and it is quite smaller (about 60 at 243 K) than that of ice Ih, probably due to the lower density of the clathrates [ Rick and Freeman , ]. The high‐frequency value, in case of nonpolar guest molecules, is comparable (about 2.9 at 243 K) with that of ice Ih, whereas it becomes higher if the guest molecules are polar (see Table ).…”

Section: Dielectric Properties Of Hydrates and Icy Mixturesmentioning

confidence: 95%

Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

Pettinelli

Cosciotti

Paolo

et al. 2015

Reviews of Geophysics

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The first European mission dedicated to the exploration of Jupiter and its icy moons (JUpiter ICy moons Explorer-JUICE) will be launched in 2022 and will reach its final destination in 2030. The main goals of this mission are to understand the internal structure of the icy crusts of three Galilean satellites (Europa, Ganymede, and Callisto) and, ultimately, to detect Europa's subsurface ocean, which is believed to be the closest to the surface among those hypothesized to exist on these moons. JUICE will be equipped with the 9 MHz subsurface-penetrating radar RIME (Radar for Icy Moon Exploration), which is designed to image the ice down to a depth of 9 km. Moreover, a parallel mission to Europa, which will host onboard REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface) equipped with 9MHz and 60MHz antennas, has been recently approved by NASA. The success of these experiments strongly relies on the accurate prediction of the radar performance and on the optimal processing and interpretation of radar echoes that, in turn, depend on the dielectric properties of the materials composing the icy satellite crusts. In the present review we report a complete range of potential ice types that may occur on these icy satellites to understand how they may affect the results of the proposed missions. First, we discuss the experimental results on pure and doped water ice in the framework of the Jaccard theory, highlighting the critical aspects in terms of a lack of standard laboratory procedures and inconsistency in data interpretation. We then describe the dielectric behavior of extraterrestrial ice analogs like hydrates and icy mixtures, carbon dioxide ice and ammonia ice. Building on this review, we have selected the most suitable data to compute dielectric attenuation, velocity, vertical resolution, and reflection coefficients for such icy moon environments, with the final goal being to estimate the potential capabilities of the radar missions as a function of the frequency and temperature ranges of interest for the subsurface sounders. We present the different subsurface scenarios and associated radar signal attenuation models that have been proposed so far to simulate the structure of the crust of Europa and discuss the physical and geological nature of various dielectric targets potentially detectable with RIME. Finally, we briefly highlight several unresolved issues that should be addressed, in near future, to improve our capability to produce realistic electromagnetic models of icy moon crusts. The present review is of interest for the geophysical exploration of all solar system bodies, including the Earth, where ice can be present at the surface or at relatively shallow depths.

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Section: Dielectric Properties Of Hydrates and Icy Mixturesmentioning

confidence: 95%

Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

Pettinelli

Cosciotti

Paolo

et al. 2015

Reviews of Geophysics

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“…All these structures present proton disorder. [65][66][67][68] We used the algorithm proposed by Buch et al 69 to generate proton disordered structures satisfying the Bernal-Fowler rules 70 and with zero ͑or almost zero͒ dipole moment.…”

Section: ͑7͒mentioning

confidence: 99%

Can gas hydrate structures be described using classical simulations?

Conde

Vega

McBride

et al. 2010

The Journal of Chemical Physics

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Quantum path-integral simulations of the hydrate solid structures have been performed using the recently proposed TIP4PQ/2005 model. By also performing classical simulations using this model, the impact of the nuclear quantum effects on the hydrates is highlighted; nuclear quantum effects significantly modify the structure, densities, and energies of the hydrates, leading to the conclusion that nuclear quantum effects are important not only when studying the solid phases of water but also when studying the hydrates. To analyze the validity of a classical description of hydrates, a comparison of the results of the TIP4P/2005 model (optimized for classical simulations) with those of TIP4PQ/2005 (optimized for path-integral simulations) was undertaken. A classical description of hydrates is able to correctly predict the densities at temperatures above 150 K and the relative stabilities between the hydrates and ice I(h). The inclusion of nuclear quantum effects does not significantly modify the sequence of phases found in the phase diagram of water at negative pressures, namely, I(h)-->sII-->sH. In fact the transition pressures are little affected by the inclusion of nuclear quantum effects; the phase diagram predictions for hydrates can be performed with reasonable accuracy using classical simulations. However, for a reliable calculation of the densities below 150 K, the sublimation energies, the constant pressure heat capacity, and the radial distribution functions, the incorporation of nuclear quantum effects is indeed required.

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“…The molecules occupying the cavities of the host lattice should be neither too large nor too small to yield a stable hydrate. 1,5,6 Thus, it is not possible to study empty hydrates using experimental methods since they are thermodynamically unstable, although they can be studied by computer simulation [7][8][9][10][11][12][13][14] due to their mechanical stability. In our earlier work, we performed computer simulation studies using empty hydrates to estimate the phase diagram of water at negative pressures 8 and the difference in the chemical potential between ice I h and the empty hydrates, which plays a central role within the widely used van der Waals-Platteeuw theory.…”

Section: Introductionmentioning

confidence: 99%

Determining the three-phase coexistence line in methane hydrates using computer simulations

Conde

Vega²

2010

The Journal of Chemical Physics

225

212

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Molecular dynamics simulations have been performed to estimate the three-phase (solid hydrate-liquid water-gaseous methane) coexistence line for the water-methane binary mixture. The temperature at which the three phases are in equilibrium was determined for three different pressures, namely, 40, 100, and 400 bar by using direct coexistence simulations. In the simulations water was described by using either TIP4P, TIP4P/2005, or TIP4P/Ice models and methane was described as simple Lennard-Jones interaction site. Lorentz-Berthelot combining rules were used to obtain the parameters of the cross interactions. For the TIP4P/2005 model positive deviations from the energetic Lorentz-Berthelot rule were also considered to indirectly account for the polarization of methane when introduced in liquid water. To locate the three-phase coexistence point, two different global compositions were used, which yielded (to within statistical uncertainty) the same predictions for the three-phase coexistence temperatures, although with a somewhat different time evolution. The three-phase coexistence temperatures obtained at different pressures when using the TIP4P/Ice model of water were in agreement with the experimental results. The main reason for this is that the TIP4P/Ice model reproduces the melting point of ice I(h).

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Proton disorder and the dielectric constant of type II clathrate hydrates

Cited by 19 publications

References 59 publications

Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

Can gas hydrate structures be described using classical simulations?

Determining the three-phase coexistence line in methane hydrates using computer simulations

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