In Situ Experimental Evidence for a Nonmonotonous Structural Evolution with Composition in the Molten LiF−ZrF<sub>4</sub> System

Pauvert, Olivier; Zanghi, Didier; Salanne, Mathieu; Simon, Christian; Rakhmatullin, Aydar; Matsuura, Haruaki; Okamoto, Yoshihiro; Vivet, François; Bessada, Catherine

doi:10.1021/jp912195j

Cited by 67 publications

(71 citation statements)

References 58 publications

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“…The intensity of this first peak slowly increases with the YF 3 concentration. This evolution is linked to the slow increase in average CN discussed just above and shown in the bottom panel of fluorozirconates 34,42,47 . Such a structural feature, which denotes some medium-range, network-like ordering, has been shown to impact importantly the transport properties in molten fluorides.…”

Section: Microscopic Structurementioning

confidence: 78%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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The transport properties of molten LiF-YF 3 mixtures have been studied by pulsed field gradient nuclear magnetic resonance spectroscopy, potentiometric experiments, and molecular dynamics simulations. The calculated diffusion coefficients and electric conductivities compare very well with the measurements across a wide composition range. We then extract static (radial distribution functions, coordination numbers distributions) and dynamic (cage correlation functions) quantities from the simulations. Then, we discuss the interplay between the microscopic structure of the molten salts and their dynamic properties. It is often considered that variations in the diffusion coefficient of the anions are mainly driven by the evolution of its coordination with the metallic ion (Y 3+ here). We compare this system with fluorozirconate melts and demonstrate that the coordination number is a poor indicator of the evolution of the diffusion coefficient. Instead, we propose to use the ionic bonds lifetime. We show that the weak Y-F ionic bonds in LiF-YF 3 do not induce the expected tendency of the fluoride diffusion coefficient to converge toward the one of yttrium cation when the content in YF 3 increases. Implications on the validity of the Nernst-Einstein relation for estimating the electrical conductivity are discussed.

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Section: Microscopic Structurementioning

confidence: 78%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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“…This allowed us to predict heat-transport properties of LiFNaF-KF and NaF-ZrF 4 mixtures 38 in order to evaluate their suitability to serve as primary coolant in the advanced high-temperature reactor concept. 92 Our simulations were also used to interpret EXAFS and NMR experimental data on fluorozirconate melts 93 and to calculate electrical conductivities 94 , diffusion coefficients 95 and internal mobilities 96 .…”

Section: Obtaining the Parameters From Force-matching And Multipmentioning

confidence: 99%

Including many-body effects in models for ionic liquids

Salanne¹,

Rotenberg²,

Jahn³

et al. 2012

Theor Chem Acc

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118

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Realistic modeling of ionic systems necessitates taking explicitly account of many-body effects. In molecular dynamics simulations, it is possible to introduce explicitly these effects through the use of additional degrees of freedom. Here we present two models: The first one only includes dipole polarization effect, while the second also accounts for quadrupole polarization as well as the effects of compression and deformation of an ion by its immediate coordination environment. All the parameters involved in these models are extracted from first-principles density functional theory calculations. This step is routinely done through an extended force-matching procedure, which has proven to be very succesfull for molten oxides and molten fluorides. Recent developments based on the use of localized orbitals can be used to complement the force-matching procedure by allowing for the direct calculations of several parameters such as the individual polarizabilities.

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“…Recent structural studies on rare earth/actinide (and analogous cations) alkali fluoride mixtures have shown that the liquid behaves like a labile network. 39,40,41,42 On the reverse, molten alkali fluorides and their mixtures typify basic molten salts. Their viscosity is known to be of the same order of magnitude than liquid water, which means that these liquids are highly fluid.…”

Section: Introductionmentioning

confidence: 99%

Evidence of dynamical local scale distribution heterogeneities in CsF-AF (A=Li, Na, K and Rb) molten salts

Rollet

Bessada

2015

Journal of Fluorine Chemistry

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International audienceThe local structure of molten CsF-AF (A = Li, Na, K and Rb) has been studied by high temperature Nuclear Magnetic Resonance (NMR) spectroscopy. The 19F and 133Cs chemical shifts have been measured as a function of the molar fraction of CsF. 19F chemical shift varies linearly with composition while 133Cs chemical shift presents a break around the eutectics composition. Furthermore, in molten CsF-LiF at high CsF concentration, 133Cs chemical shift is nearly constant. The evolutions of 19F and 133Cs chemical shifts versus CsF-AF composition have been interpreted as a signature of dynamical local scale distribution heterogeneities

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In Situ Experimental Evidence for a Nonmonotonous Structural Evolution with Composition in the Molten LiF−ZrF₄ System

Cited by 67 publications

References 58 publications

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Including many-body effects in models for ionic liquids

Evidence of dynamical local scale distribution heterogeneities in CsF-AF (A=Li, Na, K and Rb) molten salts

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In Situ Experimental Evidence for a Nonmonotonous Structural Evolution with Composition in the Molten LiF−ZrF4 System

Cited by 67 publications

References 58 publications

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Including many-body effects in models for ionic liquids

Evidence of dynamical local scale distribution heterogeneities in CsF-AF (A=Li, Na, K and Rb) molten salts

Contact Info

Product

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In Situ Experimental Evidence for a Nonmonotonous Structural Evolution with Composition in the Molten LiF−ZrF₄ System