Thermodynamic Properties of Liquid Non‐Metallic NaNaBr Solutions

Egan, J. J.; Freyland, W.

doi:10.1002/bbpc.19850890406

Cited by 28 publications

(7 citation statements)

References 13 publications

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“…Previous studies 1-7 have established that various defect states such as polarons, bipolarons, and Drudetype electrons are formed when M -MX mixtures are heated just above the melting point of the pure salt. Qualitatively, these observations could be explained by a thermodynamic defect model, 15 which is basically in line with a simple two component model describing highly doped semiconductors. The formation of bipolaron species in M -MX mixtures was first predicted by molecular dynamics calculations by Parrinello and coworkers 8,11 and confirmed experimentally by Freyland and co-workers.…”

Section: Introductionsupporting

confidence: 67%

“…Furthermore, our results together with those in Na-NaI and K-KCl melts 5,6 support a simple thermodynamic model proposed by Egan and Freyland 15 to explain the properties of electronic defects in M -MX molten solutions. According to the defect model, 15 various electronic defects ͑polarons, bipolarons, and Drude-type electrons͒ in M -MX molten solutions continuously interact with each other on a time scale on the order of 10 −12 s. On the one hand, the asymmetric broadening of the absorption band in M -MX mixtures is caused by the fluctuations of the Madelung 12,35 potential due to liquid state disorders. 1 that in the case of Cs-CsI melt, the excess electrons are excited in the blue part ͑shifted by 0.71 eV with respect to the peak position͒ of the absorption spectrum compared to a slight redshift by 0.07 eV in Na-NaI melts.…”

Section: Blue-part Versus Red-part Excitationmentioning

confidence: 99%

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Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide

Chandrasekhar

Unterreiner

2007

The Journal of Chemical Physics

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Temperature-dependent investigations of excess electrons in molten solutions of cesium-doped cesium iodide (Cs-CsI) (mole fraction of Cs approximately 0.003) were performed applying femtosecond pump-probe absorption spectroscopy. The pulse-limited induced bleach observed at probe wavelengths from 600 to 1240 nm was attributed to the excitation of equilibrated excess electrons which were initially formed by melting a Cs-CsI mixture. The interpretation of the relaxation process is based on strongly localized polarons that constitute the majority of defect states in this melt. As expected, the bipolaron contribution was insignificant. The time constants (tau1) were found to be temperature dependent confirming our earlier findings in Na-NaI melts that ionic diffusion almost exclusively controls the dynamics of excess electrons in high temperature ionic liquids. Apart from this temperature dependence, the relaxation dynamics of excess electrons do not differ irrespective of the excitation regime (blue or red part of the respective stationary spectra).

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Section: Introductionsupporting

confidence: 67%

Section: Blue-part Versus Red-part Excitationmentioning

confidence: 99%

Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide

Chandrasekhar

Unterreiner

2007

The Journal of Chemical Physics

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“…For numerical purposes, we must assume small, but non-zero values for the reference concentrations of the electroinactive species, equivalent to assuming large (positive or negative), but finite, values for their standard potentials. In reality these concentrations are not zero, as might be indicated by an electrolyte with electronic conductivity or an electrode with some anion solubility [2,17,18].…”

Section: B Standard Chemical Potentialsmentioning

confidence: 99%

Phase field modeling of electrochemistry. I. Equilibrium

et al. 2004

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A diffuse interface (phase field) model for an electrochemical system is developed. We describe the minimal set of components needed to model an electrochemical interface and present a variational derivation of the governing equations. With a simple set of assumptions: mass and volume constraints, Poisson's equation, ideal solution thermodynamics in the bulk, and a simple description of the competing energies in the interface, the model captures the charge separation associated with the equilibrium double layer at the electrochemical interface. The decay of the electrostatic potential in the electrolyte agrees with the classical Gouy-Chapman and Debye-Hückel theories. We calculate the surface free energy, surface charge, and differential capacitance as functions of potential and find qualitative agreement between the model and existing theories and experiments. In particular, the differential capacitance curves exhibit complex shapes with multiple extrema, as exhibited in many electrochemical systems.

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“…5,6,14,15 Such electrons are neither strongly localized nor completely free and are characterized as Drudetype electrons. Freyland and Egan 16 first described these observations consistently by a dynamical equilibrium between localized and mobile electrons: In M-MX solutions at high temperatures the local fluctuations of the potential energy influence the potential well of the liquid F-centre. As a result, the excess electron may escape through a thermally activated hopping process before it is re-localized in an adjacent site.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of excess electrons in molten salts: Part II. Femtosecond investigations of Na–NaBr and Na–NaI melts

Brands

Chandrasekhar

Hippler

et al. 2005

Phys. Chem. Chem. Phys.

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Ultrafast dynamics of excess electrons in Na-NaBr and Na-NaI molten solutions at elevated temperatures (T = 953-1128 K) were investigated over an extended wavelength range. Modelling the time profiles resulted in two time constants tau 1 = (200 +/- 40) fs and tau 2 = (2.8 +/- 0.4) ps for both systems at 1073 K. All transients can be understood in terms of dynamical equilibria between polaron and Drude-type electrons as well as polaron and Drude-type electron forming bipolarons. In agreement with our earlier results for K-KCl melts the fast component is assigned to the relaxation of Drude-type electrons into polarons while the longer component, tau 2, represents the time during which Drude-type electrons recombine with polarons leading to bipolarons. In addition, the temperature dependence was studied in Na-Nal: Decreasing the temperature to 953 K resulted in an increase of the time constants to tau 1 = (360 +/- 50) fs and tau 2 = (4.3 +/- 0.7) ps, respectively. At temperatures, where the ionic diffusion in Na-NaI melts becomes comparable to Na-NaBr melts, the time constants for the relaxation processes also coincide. The temperature-dependent investigations resulted in an Arrhenius activation energy of (25 +/- 5) kJ mol(-1) for Na-NaI melts in good agreement with literature data.

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Thermodynamic Properties of Liquid Non‐Metallic NaNaBr Solutions

Cited by 28 publications

References 13 publications

Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide

Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide

Phase field modeling of electrochemistry. I. Equilibrium

Ultrafast dynamics of excess electrons in molten salts: Part II. Femtosecond investigations of Na–NaBr and Na–NaI melts

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