A new approach for coupled modelling of the structural and thermo-physical properties of molten salts. Case of a polymeric liquid LiF-BeF2

Smith, Anna; Capelli, E.; Konings, R.J.M.; Gheribi, Aïmen E.

doi:10.1016/j.molliq.2019.112165

Cited by 50 publications

(35 citation statements)

References 47 publications

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“…Weighted least square regression was used to obtain a linear trend between specific enthalpies and temperature for each composition. A similar linear trend in specific enthalpies and temperature for short temperature ranges (200 °C-300 °C) at higher temperatures (>T melt ) was noticed in previous literature [13,[39][40][41][42][43], while a nonlinear relationship was obtained when fitting to a wider temperature range [37,38,44,45]. For composition C, a second-order polynomial fit better described the specific enthalpies and temperature trend in temperature range of 700 °C-900 °C (Figure 11C).…”

Section: Specific Heat Capacitysupporting

confidence: 86%

“…It can be noted that even after significantly longer simulation times, the stress ACF is not converging to zero, hence delaying the plateau behavior in the viscosity values. It is also observed by other researchers while simulating a highly polymerized system such as LiF-BeF 2 [37]. Figure 10 reports the ACF and viscosity values evaluated from Eq.…”

Section: Viscositysupporting

confidence: 71%

“…As such, no experimental data for viscosities are available for comparison for compositions A and B. As previously observed for Flibe [37] and NaF-ZrF 4 [38], viscosity values tend to decrease with the decrease in the mol% of networkforming multivalent cations. Following such trend, the viscosity values for composition A would be expected to be lower than the experimental value of 6.9 cP for composition C. A comparatively higher value of viscosity calculated from the RIM simulation of composition A can be due to the higher coordination number of Zr (Table 1) and short-lived chain formation involving ~27% of Zr in the melt (Table 3).…”

Section: Viscositymentioning

confidence: 99%

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Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

2022

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LiF–NaF–ZrF4 multicomponent molten salts are identified as promising candidates for coolant salts in molten salt reactors and advanced high-temperature reactors. This study focused on low-melting point salt compositions of interest: 38LiF–51NaF–11ZrF4, 42LiF–29NaF–29ZrF4, and 26LiF–37NaF–37ZrF4. Ab-initio molecular dynamics (AIMD) calculations were performed and compared with available experimental data to assess the ability of rigid ion models (RIM) to reproduce short- to intermediate-range structure, transport, and thermophysical properties of the LiF–NaF–ZrF4 salt mixtures. It is found that as ZrF4 mol% increases, the average cation–anion coordination number (CN) of monovalent cations (Li+, Na+) obtained from RIM calculations decreases, while multivalent Zr4+ CN varied from 15% to 19% in comparison to corresponding AIMD values. In addition, RIM is found to predict the existence of 7, 8, and 9 coordinated fluorozirconate complexes, while AIMD and the available experimental data showed an occurrence of 6, 7, and 8 coordinated complexes in the melt. The intermediate-range structure analysis revealed that while the RIM parameters are able to reproduce a local structure for lower ZrF4 mol% salts such as in 38LiF–51NaF–11ZrF4, an extensive fluorozirconate network formation is observed in RIM simulations for higher ZrF4 mol% compositions. The network generated by RIM parameters is found to be mainly connected by “corner-sharing” fluorozirconate complexes as opposed to both “edge-sharing” and “corner-sharing” connectively portrayed by AIMD. It is found that a close agreement between AIMD and the RIM salt structure for the 11-mol% ZrF4 salt resulted in good agreement in the calculated Zr diffusivities and the viscosity values. However, due to the inaccurate short- to intermediate-range structure prediction by RIM for higher ZrF4 mol% compositions, thermophysical properties such as densities and heat capacity differ by up to 26% and 27%, respectively, upon comparison with AIMD and experimental values. Also, the network-dominated properties such as diffusion coefficients and viscosities differed by up to two and three orders of magnitude, respectively. This study signifies the importance of accurate salt structure generation for an accurate prediction of transport and thermophysical properties of multicomponent molten salts.

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Section: Specific Heat Capacitysupporting

confidence: 86%

Section: Viscositysupporting

confidence: 71%

Section: Viscositymentioning

confidence: 99%

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Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

2022

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“…Despite its practicality, structural features, such as molecular species and network formation, are not accounted for. However, structural features may be imposed on the model, for example by explicitly introducing ions with different coordinations [40,41]. In this formalism, a set of two anions and two cations makes up a quadruplet, taken to be the basic unit in the liquid solution, and the excess parameters to be optimised are those related to the following second-nearest neighbour (SNN) exchange reaction:…”

Section: Liquid Solutionmentioning

confidence: 99%

Thermodynamic Description of the ACl-ThCl4 (A = Li, Na, K) Systems

Flores

Rooijakkers

Konings

et al. 2021

Thermo

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The ACl-ThCl4 (A = Li, Na, K) systems could be of relevance to the nuclear industry in the near future. A thermodynamic investigation of the three binary systems is presented herein. The excess Gibbs energy of the liquid solutions is described using the quasi-chemical formalism in the quadruplet approximation. The phase diagram optimisations are based on the experimental data available in the literature. The thermodynamic stability of the liquid solutions increases in the order Li < Na < K, in agreement with idealised interactions and structural models.

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“…The excess Gibbs energy terms of the (Na,Th)F x liquid solution have been modeled in the present work using a modified quasi-chemical model similar to the one recently optimized for the LiF–BeF 2 system. 47 A detailed description is given in Supporting Information . As will be examined in the following sections, (Na,Th)F x is not a solution in which cations and anions are completely dissociated.…”

Section: Methodsmentioning

confidence: 99%

Experimental and Computational Exploration of the NaF–ThF₄ Fuel System: Structure and Thermochemistry

et al. 2021

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The structural, thermochemical, and thermophysical properties of the NaF–ThF 4 fuel system were studied with experimental methods and molecular dynamics (MD) simulations. Equilibrium MD (EMD) simulations using the polarizable ion model were performed to calculate the density, molar volume, thermal expansion, mixing enthalpy, heat capacity, and distribution of [ThF n ] m − complexes in the (Na,Th)F x melt over the full concentration range at various temperatures. The phase equilibria in the 10–50 mol % ThF 4 and 85–95 mol % ThF 4 regions of the NaF–ThF 4 phase diagram were measured using differential scanning calorimetry, as were the mixing enthalpies at 1266 K of (NaF/ThF 4 ) = (0.8:0.2), (0.7:0.3) mixtures. Furthermore, the β-Na 2 ThF 6 and NaTh 2 F 9 compounds were synthesized and subsequently analyzed with the use of X-ray diffraction. The heat capacities of both compounds were measured in the temperature ranges (2–271 K) and (2–294 K), respectively, by thermal relaxation calorimetry. Finally, a CALPHAD model coupling the structural and thermodynamic data was developed using both EMD and experimental data as input and a quasichemical formalism in the quadruplet approximation. Here, 7- and 8-coordinated Th 4+ cations were introduced on the cationic sublattice alongside a 13-coordinated dimeric species to reproduce the chemical speciation, as calculated by EMD simulations and to provide a physical description of the melt.

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A new approach for coupled modelling of the structural and thermo-physical properties of molten salts. Case of a polymeric liquid LiF-BeF2

Cited by 50 publications

References 47 publications

Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

Thermodynamic Description of the ACl-ThCl4 (A = Li, Na, K) Systems

Experimental and Computational Exploration of the NaF–ThF₄ Fuel System: Structure and Thermochemistry

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A new approach for coupled modelling of the structural and thermo-physical properties of molten salts. Case of a polymeric liquid LiF-BeF2

Cited by 50 publications

References 47 publications

Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

Short- to Intermediate-Range Structure, Transport, and Thermophysical Properties of LiF–NaF–ZrF4 Molten Salts

Thermodynamic Description of the ACl-ThCl4 (A = Li, Na, K) Systems

Experimental and Computational Exploration of the NaF–ThF4 Fuel System: Structure and Thermochemistry

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Product

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About

Experimental and Computational Exploration of the NaF–ThF₄ Fuel System: Structure and Thermochemistry