Metastable extension of the liquid-vapor phase equilibrium curve and surface tension

Байдаков, В. Г.; Проценко, С. П.; Kozlova, Z.R.; Черных, Г. Г.

doi:10.1063/1.2734964

Cited by 66 publications

(82 citation statements)

References 22 publications

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“…We refer to a molecular dynamics study by Baidakov et al [53] to provide values of the saturated vapour density ρ vs and liquid density ρ l = 1/v l of the argon-like Lennard-Jones fluid at a temperature of 60.31 K. Figure 8 shows our excess free energies F s (i) as a function of cluster size i. Statistical errors propagated from uncertainties in the free energy change ∆F are similar to the size of the symbols.…”

Section: B Results and Discussionmentioning

confidence: 99%

Free energies of molecular clusters determined by guided mechanical disassembly

Tang

Ford

2015

Phys. Rev. E

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The excess free energy of a molecular cluster is a key quantity in models of the nucleation of droplets from a metastable vapour phase; it is often viewed as the free energy arising from the presence of an interface between the two phases. We show how this quantity can be extracted from simulations of the mechanical disassembly of a cluster using guide particles in molecular dynamics. We disassemble clusters ranging in size from 5 to 27 argon-like Lennard-Jones atoms, thermalised at 60 K, and obtain excess free energies, by means of the Jarzynski equality, that are consistent with previous studies. We only simulate the cluster of interest, in contrast to approaches that require a series of comparisons to be made between clusters differing in size by one molecule. We discuss the advantages and disadvantages of the scheme and how it might be applied to more complex systems.

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Section: B Results and Discussionmentioning

confidence: 99%

Free energies of molecular clusters determined by guided mechanical disassembly

Tang

Ford

2015

Phys. Rev. E

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“…coordination number n coor.no. = 7 of the particle nearest the center of mass of the nucleus corresponds to a density ρ ≈ 0.60, which is equal to the density of the critical cluster at a much higher temperature [10], but significantly below the bulk density of LJ liquid ( ρ tr.p (l) = 0.8 and ρ(l)= 0.92 (extrapolated) at T = 0.50) [18]. The interior of the 25 critical nuclei with ρ ≈ 0.60 corresponds to a diluted liquid with only a weak ordering of a first coordination shell [19].…”

Section: Aturementioning

confidence: 99%

Nucleation and droplet growth from supersaturated vapor at temperatures below the triple point temperature

Toxværd

2016

The Journal of Chemical Physics

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In 1897 Ostwald formulated his step rule for formation of the most stable crystal state for a system with crystal polymorphism. The rule describes the irreversible way a system converts to the crystal with lowest free energy. But in fact the irreversible way a supercooled gas below the triple point temperature T tr.p. crystallizes via a liquid droplet is an example of Ostwald's step rule.The homogeneous nucleation in the supersaturated gas is not to a crystal, but to a liquid-like critical nucleus. We have for the first time performed constant energy (NVE) Molecular Dynamics (MD) of homogeneous nucleation without the use of a thermostat. The simulations of homogeneous nucleation in a Lennard-Jones system from supersaturated vapor at temperatures below T tr.p. reveals that the nucleation to a liquid-like critical nucleus is initiated by a small cold cluster [S.Toxvaerd, J. Chem. Phys. 143 154705 (2015)]. The release of latent heat at the subsequent droplet growth increases the temperature in the liquid-like droplet, which for not deep supercooling and/or low supersaturation, can exceed T tr.p. . The temperature of the liquid-like droplet increases less for a low supersaturation and remains below T tr.p. , but without a crystallization of the droplet for long times. The dissipation of the latent heat into the surrounding gas is affected by a traditional MD thermostat, with the consequence that droplet growth is different for (NVE) MD and constant temperature (NVT) MD.

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“…The thermodynamic properties of the LJ fluid depend on the cutoff scale. [47][48][49][50] The scale of 5σ is widely used in nucleation simulations 13,21,22,51 and the resulting fluid comes relatively close to the full potential LJ-fluid and to real argon [47][48][49][50]52 at a reasonable computational cost. In Sec.…”

Section: A Simulation Code Setup and Parametersmentioning

confidence: 99%

“…13,21,22,51 The thermodynamic properties of the LJ fluid depend on the cutoff scale, especially the surface tension of a fluid with a 5σ cutoff lie a few percent below the 6.78σ cutoff values and the full potential values. [47][48][49][50] For the comparisons with theoretical models, we use surface tension values from Ref. 50, who used a 6.78σ cutoff.…”

Section: Numerical Convergence Testsmentioning

confidence: 99%

Large scale molecular dynamics simulations of homogeneous nucleation

Diemand

Angélil

Tanaka

et al. 2013

The Journal of Chemical Physics

118

163

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We present results from large-scale molecular dynamics (MD) simulations of homogeneous vapor-to-liquid nucleation. The simulations contain between 1 × 109 and 8 × 109 Lennard-Jones (LJ) atoms, covering up to 1.2 s (56 × 106 time-steps). They cover a wide range of supersaturation ratios, S = 1.55-104, and temperatures from kT = 0.3 to 1.0 (where is the depth of the LJ potential, and k is the Boltzmann constant). We have resolved nucleation rates as low as 1017 cm-3 s-1 (in the argon system), and critical cluster sizes as large as 100 atoms. Recent argon nucleation experiments probe nucleation rates in an overlapping range, making the first direct comparison between laboratory experiments and molecular dynamics simulations possible: We find very good agreement within the uncertainties, which are mainly due to the extrapolations of argon and LJ saturation curves to very low temperatures. The self-consistent, modified classical nucleation model of Girshick and Chiu [J. Chem. Phys. 93, 1273 (1990)] underestimates the nucleation rates by up to 9 orders of magnitudes at low temperatures, and at kT = 1.0 it overestimates them by up to 105. The predictions from a semi-phenomenological model by Laaksonen et al. [Phys. Rev. E 49, 5517 (1994)] are much closer to our MD results, but still differ by factors of up to 104 in some cases. At low temperatures, the classical theory predicts critical clusters sizes, which match the simulation results (using the first nucleation theorem) quite well, while the semi-phenomenological model slightly underestimates them. At kT = 1.0 , the critical sizes from both models are clearly too small. In our simulations the growth rates per encounter, which are often taken to be unity in nucleation models, lie in a range from 0.05 to 0.24. We devise a new, empirical nucleation model based on free energy functions derived from subcritical cluster abundances, and find that it performs well in estimating nucleation rates. We present results from large-scale molecular dynamics (MD) simulations of homogeneous vapor-toliquid nucleation. The simulations contain between 1 × 10 9 and 8 × 10 9 Lennard-Jones (LJ) atoms, covering up to 1.2 μs (56 × 10 6 time-steps). They cover a wide range of supersaturation ratios, S 1.55-10 4 , and temperatures from kT = 0.3 to 1.0 (where is the depth of the LJ potential, and k is the Boltzmann constant). We have resolved nucleation rates as low as 10 17 cm −3 s −1 (in the argon system), and critical cluster sizes as large as 100 atoms. Recent argon nucleation experiments probe nucleation rates in an overlapping range, making the first direct comparison between laboratory experiments and molecular dynamics simulations possible: We find very good agreement within the uncertainties, which are mainly due to the extrapolations of argon and LJ saturation curves to very low temperatures. The self-consistent, modified classical nucleation model of Girshick and Chiu [J. Chem. Phys. 93, 1273 (1990)] underestimates the nucleation rates by up to 9 orders of magnitudes at l...

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Metastable extension of the liquid-vapor phase equilibrium curve and surface tension

Cited by 66 publications

References 22 publications

Free energies of molecular clusters determined by guided mechanical disassembly

Free energies of molecular clusters determined by guided mechanical disassembly

Nucleation and droplet growth from supersaturated vapor at temperatures below the triple point temperature

Large scale molecular dynamics simulations of homogeneous nucleation

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