Theory of transport in liquid metals. I. Calculation of self-diffusion coefficients

Protopapas, Pavlos; Andersen, Hans Christian; Parlee, N. A. D.

doi:10.1063/1.1679784

Cited by 252 publications

(155 citation statements)

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“…15 Between T f and T m the nanoparticle fluctuates between the solid and liquid states 32,37,38 and overall resembles a viscous droplet of atoms. 26,27 ), the T range of dynamic coexistence enhances this diffusion, Figure 2. Figure 2a shows T m of Fe N for N ϭ 50Ϫ256 (d Ϸ 1Ϫ1.7 nm).…”

mentioning

confidence: 99%

Viscous State Effect on the Activity of Fe Nanocatalysts

Cervantes‐Sodi

McNicholas²,

Simmons³

et al. 2010

ACS Nano

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C atalytic chemical vapor deposition (CVD) is an effective site/sizeselective synthesis technique. 1Ϫ7The properties of the catalytic particle play a key role in the nucleation and growth processes, as well as in the final nanostructure morphology. 7Ϫ11 At the nanoscale, two aspects are inter-related: the possibility of bulk and surface diffusion of the feedstock in and on the nanoparticles 12Ϫ14 and the thermody- Here, we analyze the nanoparticles near the melting point by investigating, as functions of size, the melting depression and the self-diffusion coefficient D leading to viscosity ( ϰ 1/D). RESULTS AND DISCUSSIONIn nanoparticles, the melting point is inversely proportional to the diameter through the GibbsϪThomson (GT) relation. 9,19,21,22 We describe this by using classical molecular dynamics (MD) (see Methods for details). We characterize the melting by the change in internal energy, with associated latent heat, and by the variation in the Lindemann index statisticalbond-length order parameter, ␦, with respect to the temperature T.

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mentioning

confidence: 99%

Viscous State Effect on the Activity of Fe Nanocatalysts

Cervantes‐Sodi

McNicholas²,

Simmons³

et al. 2010

ACS Nano

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“…A further quantitative test of the MCT was done recently on the dynamics of liquid titanium [26] (see figure 8a). Instead of the structure factor in equation (8) experimental structure factors were used as input with only the high q-range fitted to hard sphere structure factor similar to equation (8). This was necessary, because the compressibility limit S(q = 0) in the PY approximations turns out to be about twice as high compared to the experimental values [31].…”

Section: Resultsmentioning

confidence: 99%

“…Efforts were made to describe the liquid dynamics as well in terms of that of the hard-sphere liquid, using generalizations of Enskog's kinetic theory [3,4,7]. The single-particle (incoherent) dynamics of liquid metals could have accounted for a successful combination of Enskog theory and molecular-dynamics results [8]. There are also attempts to describe the collective dynamics in terms of the hard-sphere dynamics [9].…”

Section: Introductionmentioning

confidence: 99%

Collective dynamics of simple liquids: A mode-coupling description

Schirmacher¹,

Sinn²

2008

Condens. Matter Phys.

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We use the mode-coupling theory (MCT), which has been highly successful in accounting for the anomalous relaxation behaviour near the liquid-to-glass transition, for describing the dynamics of monatomic (i.e. simple) liquids away from the glass formation regime. We find that the dynamical structure factor predicted by MCT compares well to experimental findings and results of computer simulations. The memory function exhibits a two-step decay as found frequently in experimental and simulation data. The long-time relaxation regime, in which the relaxation rate strongly depends on the density and is identified as the α relaxation. At high density this process leads the glass instability. The short-time relaxation rate is fairly independent of density.

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“…The rationale for the hypothesized higher permeance of SMMM may be understood within the framework of the so-called Sieverts law A key argument for SMMM is a substantially higher diffusion coefficient for H atoms in liquid metal (Protopapas et al, 1973) as compared to that in a solid metal (Wert and Zener, 1949 Step change in hydrogen solubility of a metal upon melting (Nakajima, 2007).…”

Section: Hypothesismentioning

confidence: 99%

Supported Molten Metal Membranes for Hydrogen Separation

Datta¹,

Hua²,

Yen³

et al. 2013

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We describe here our results on the feasibility of a novel dense metal membrane for hydrogen separation: Supported Molten Metal Membrane, or SMMM. 1 The goal in this work was to develop these new membranes based on supporting thin films of low-melting, nonprecious group metals, e.g., tin (Sn), indium (In), gallium (Ga), or their alloys, to provide a flux and selectivity of hydrogen that rivals the conventional but substantially more expensive palladium (Pd) or Pd alloy membranes, which are susceptible to poisoning by the many species in the coal-derived syngas, and further possess inadequate stability and limited operating temperature range. The novelty of the technology presented numerous challenges during the course of this project, however, mainly in the selection of appropriate supports, and in the fabrication of a stable membrane. While the wetting instability of the SMMM remains an issue, we did develop an adequate understanding of the interaction between molten metal films with porous supports that we were able to find appropriate supports. Thus, our preliminary results indicate that the Ga/SiC SMMM at 550 ºC has a permeance that is an order of magnitude higher than that of Pd, and exceeds the 2015 DOE target.To make practical SMM membranes, however, further improving the stability of the molten metal membrane is the next goal. For this, it is important to better understand the change in molten metal surface tension and contact angle as a function of temperature and gas-phase composition. A thermodynamic theory was, thus, developed, 2 that is not only able to explain this change in the liquid-gas surface tension, but also the change in the solid-liquid surface tension as well as the contact angle. This fundamental understanding has allowed us to determine design characteristics to maintain stability in the face of changing gas composition. These designs are being developed. For further progress, it is also important to understand the nature of solution and permeation process in these molten metal membranes. For this, a comprehensive microkinetic model was developed for hydrogen permeation in dense metal membranes, and tested against data for Pd membrane over a broad range of temperatures.3 It is planned to obtain theoretical and experimental estimates of the parameters to corroborate the model against experimental results for SMMM.1 Datta, R., and Yen, P.-S., "Hydrogen Separation Membrane," Patent Application filed (2013). 2 Yen, P.-S., and Datta, R., "Butler-Sugimoto Monomolecular Bilayer Interface Model: The Effect of Oxygen on the Surface Tension of a Liquid Metal and its Wetting of a Ceramic," submitted to J. Colloid & Interf. Sci. (2014 References …………………………………………………………….…………………39 5 MotivationThe defining challenge of our time is to find a way to meet the growing need for energy of an increasingly populous and prosperous world without putting the planet in peril. The solution will undoubtedly involve a combination of energy sources. Nonetheless, hydrogen, whether from fossil or renewable r...

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Theory of transport in liquid metals. I. Calculation of self-diffusion coefficients

Cited by 252 publications

References 30 publications

Viscous State Effect on the Activity of Fe Nanocatalysts

Viscous State Effect on the Activity of Fe Nanocatalysts

Collective dynamics of simple liquids: A mode-coupling description

Supported Molten Metal Membranes for Hydrogen Separation

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