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R Strey - One of the best experts on this subject based on the ideXlab platform.
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Nucleation Rate isotherms of argon from molecular dynamics simulations
Journal of Chemical Physics, 2007Co-Authors: Jan Wedekind, Judith Wolk, David Reguera, R StreyAbstract:We report six Nucleation Rate isotherms of vapor-liquid Nucleation of Lennard-Jones argon from molecular dynamics simulations. The isotherms span three orders of magnitude in Nucleation Rates, 1023
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measurement of the molecular content of binary nuclei iii use of the Nucleation Rate surfaces for the water n alcohol series
Journal of Chemical Physics, 1995Co-Authors: R Strey, Y Viisanen, P WagnerAbstract:In a previous paper the molecular content of binary water-n-alcohol nuclei has been determined from Nucleation Rate measurements. A strong mutual enhancement of water and alcohol in forming the nuclei was observed, although macroscopically the higher alcohols are only partially miscible with water. In this paper we replace water by n-nonane, that is, we examine n-nonane-CiH2i+1OH systems with i=2–6. Using the Nucleation pulse technique Nucleation Rates in the range 105
Nucleation of the n-alcohols with n-nonane is found, the most stubborn being ethanol. However, one observes that with increasing alcohol chain length the Nucleation process tends to become more ideal. We present the full experimental Nucleation Rate surface J(a1,a2) for n-nonane... -
measurement of the molecular content of binary nuclei ii use of the Nucleation Rate surface for water ethanol
Journal of Chemical Physics, 1994Co-Authors: Y Viisanen, R Strey, A Laaksonen, Markku KulmalaAbstract:In a preceding paper we determined the molecular contents of binary nuclei from homogeneous Nucleation Rate measurements studing ethanol–hexanol as a nearly ideal model system. Here we report the analogous measurements for the nonideal water–ethanol system known from previous investigations to display surface enrichment of ethanol in the nuclei. The Nucleation pulse technique applied allows accuRate measurements of homogeneous Nucleation Rates in the range 105
Nucleation Rates of mixed droplets in supersatuRated water–ethanol vapor mixtures with argon as the carrier gas. The experiments were performed as functions of the water and ethanol gas phase activities, a1 and a2, respectively, ranging from pure water to pure ethanol with ten intermediate activity ratios at T=260 K. The experimental data shape a Nucleation Rate surface in three‐dimensional J–a1–a2 space from which the critical activities for a Rate of Jc=107 cm−3 s−1 were determined. The critical activi... -
measurement of the molecular content of binary nuclei use of the Nucleation Rate surface for ethanol hexanol
Journal of Chemical Physics, 1993Co-Authors: R Strey, Y ViisanenAbstract:We measured the homogeneous Nucleation Rates J of mixed droplets in supersatuRated ethanol–hexanol vapor mixtures in argon as functions of the vapor phase activities a1 and a2 of ethanol and hexanol, respectively. Measurements ranged from pure ethanol to pure hexanol at T=260 K. The experimental Nucleation Rate curves shape a Nucleation Rate surface in the three‐dimensional J−a1−a2 space. We develop a theory for obtaining the average size and composition of a nucleus from this surface determined experimentally. Following this procedure experimental nucleus compositions are determined. This theory is then combined with our measurements in order to determine the makeup of the binary ethanol–hexanol nuclei. Results are compared with the predictions of classical binary Nucleation theory. Qualitatively similar trends are observed for the nearly ideal ethanol–hexanol system studied.
Y Viisanen - One of the best experts on this subject based on the ideXlab platform.
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measurement of the molecular content of binary nuclei iii use of the Nucleation Rate surfaces for the water n alcohol series
Journal of Chemical Physics, 1995Co-Authors: R Strey, Y Viisanen, P WagnerAbstract:In a previous paper the molecular content of binary water-n-alcohol nuclei has been determined from Nucleation Rate measurements. A strong mutual enhancement of water and alcohol in forming the nuclei was observed, although macroscopically the higher alcohols are only partially miscible with water. In this paper we replace water by n-nonane, that is, we examine n-nonane-CiH2i+1OH systems with i=2–6. Using the Nucleation pulse technique Nucleation Rates in the range 105
Nucleation of the n-alcohols with n-nonane is found, the most stubborn being ethanol. However, one observes that with increasing alcohol chain length the Nucleation process tends to become more ideal. We present the full experimental Nucleation Rate surface J(a1,a2) for n-nonane... -
measurement of the molecular content of binary nuclei ii use of the Nucleation Rate surface for water ethanol
Journal of Chemical Physics, 1994Co-Authors: Y Viisanen, R Strey, A Laaksonen, Markku KulmalaAbstract:In a preceding paper we determined the molecular contents of binary nuclei from homogeneous Nucleation Rate measurements studing ethanol–hexanol as a nearly ideal model system. Here we report the analogous measurements for the nonideal water–ethanol system known from previous investigations to display surface enrichment of ethanol in the nuclei. The Nucleation pulse technique applied allows accuRate measurements of homogeneous Nucleation Rates in the range 105
Nucleation Rates of mixed droplets in supersatuRated water–ethanol vapor mixtures with argon as the carrier gas. The experiments were performed as functions of the water and ethanol gas phase activities, a1 and a2, respectively, ranging from pure water to pure ethanol with ten intermediate activity ratios at T=260 K. The experimental data shape a Nucleation Rate surface in three‐dimensional J–a1–a2 space from which the critical activities for a Rate of Jc=107 cm−3 s−1 were determined. The critical activi... -
measurement of the molecular content of binary nuclei use of the Nucleation Rate surface for ethanol hexanol
Journal of Chemical Physics, 1993Co-Authors: R Strey, Y ViisanenAbstract:We measured the homogeneous Nucleation Rates J of mixed droplets in supersatuRated ethanol–hexanol vapor mixtures in argon as functions of the vapor phase activities a1 and a2 of ethanol and hexanol, respectively. Measurements ranged from pure ethanol to pure hexanol at T=260 K. The experimental Nucleation Rate curves shape a Nucleation Rate surface in the three‐dimensional J−a1−a2 space. We develop a theory for obtaining the average size and composition of a nucleus from this surface determined experimentally. Following this procedure experimental nucleus compositions are determined. This theory is then combined with our measurements in order to determine the makeup of the binary ethanol–hexanol nuclei. Results are compared with the predictions of classical binary Nucleation theory. Qualitatively similar trends are observed for the nearly ideal ethanol–hexanol system studied.
Markku Kulmala - One of the best experts on this subject based on the ideXlab platform.
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analytical formulae connecting the real and the apparent Nucleation Rate and the nuclei number concentration for atmospheric Nucleation events
Journal of Aerosol Science, 2002Co-Authors: Velimatti Kerminen, Markku KulmalaAbstract:A simple yet relatively accuRate analytical formula has been derived between the “real” atmospheric Nucleation Rate and the Rate at which the resulting clusters, or nuclei, appear at some larger size (the “apparent” Nucleation Rate) as a result of their growth by condensation. In addition, another analytical formula was derived that connects the Nucleation Rate and the total nuclei concentration in a desired size range. The derived formulae are applicable to situations in which there are no major fluctuations in the pre-existing particle size distribution or in the concentration of vapours responsible for the nuclei growth, and in which the total nuclei number concentration remains sufficiently low (<105–106 nuclei cm−3) to prevent effective self-coagulation between the nuclei. With the help of these formulae, an explicit Nucleation scheme can be included into an atmospheric model without the requirement that the modelled particle diameter range must be extended down to one nanometer. In field measurements only the “apparent” Nucleation Rate can currently be determined. The derived formulae provide a means to convert this Rate to a “real” Nucleation Rate, making it possible to test more rigorously the viability of different Nucleation theories under atmospheric conditions.
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the potential for atmospheric mixing processes to enhance the binary Nucleation Rate
Journal of Geophysical Research, 1998Co-Authors: Douglas E Nilsson, Markku KulmalaAbstract:The formation of sulfate aerosol particles due to atmospheric mixing processes is investigated using a classical model for binary Nucleation. The Nucleation Rate is seen to be enhanced when two air parcels with different temperature and relative humidity mix with each other. This is due to the curvature on the vapor pressure diagram, and the whole process is more enhanced in the binary H2SO4 - H2O system when compared with the unary case. If the differences are, for example, 8 K and 60%, the Nucleation Rate can increase by 2 to 3 orders of magnitude if they are mixed. A brief survey of atmospheric situations that could favor this process is included. The negative feedback effects of coagulation and condensation on the new aerosol particles are found to deceleRate the particle formation, but not to prevent it. The damping effect of condensation on preexisting aerosols is examined. It is found that the mixing process is most likely to be important at background conditions, which are the most difficult for explaining Nucleation. The mixing effect is also compared with the effect of fluctuations in temperature and relative humidity. In some cases the mixing effect seems to be the most important of the effects. The differences in the effect of mixing on Nucleation Rate and the limitations of its validity are given for different initial conditions. A simple parameterization of the effect of atmospheric mixing on the binary homogeneous Nucleation Rate of H2SO4 and H2O is also given.
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measurement of the molecular content of binary nuclei ii use of the Nucleation Rate surface for water ethanol
Journal of Chemical Physics, 1994Co-Authors: Y Viisanen, R Strey, A Laaksonen, Markku KulmalaAbstract:In a preceding paper we determined the molecular contents of binary nuclei from homogeneous Nucleation Rate measurements studing ethanol–hexanol as a nearly ideal model system. Here we report the analogous measurements for the nonideal water–ethanol system known from previous investigations to display surface enrichment of ethanol in the nuclei. The Nucleation pulse technique applied allows accuRate measurements of homogeneous Nucleation Rates in the range 105
Nucleation Rates of mixed droplets in supersatuRated water–ethanol vapor mixtures with argon as the carrier gas. The experiments were performed as functions of the water and ethanol gas phase activities, a1 and a2, respectively, ranging from pure water to pure ethanol with ten intermediate activity ratios at T=260 K. The experimental data shape a Nucleation Rate surface in three‐dimensional J–a1–a2 space from which the critical activities for a Rate of Jc=107 cm−3 s−1 were determined. The critical activi...
Howard Reiss - One of the best experts on this subject based on the ideXlab platform.
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Nucleation Rates in a New Phenomenological Model
Journal of Physical Chemistry B, 2006Co-Authors: Roya Zandi, David Reguera, Howard ReissAbstract:In this paper we develop a new theory to evaluate the Nucleation Rate in the framework of the EMLD-DNT model. Beyond the model, our theory deals with cluster translation and exclusion, effects that have been virtually ignored in classical Nucleation theory. We apply the model to the case of 1-pentanol, and compare the predictions with experimental results. We find an excellent agreement between the Nucleation Rate predicted by our theory and experimental data. The distinguishing feature of the model is its ability to predict successfully the Rate of formation of the critical nucleus without the use of an intermolecular potential, employing only macroscopic thermodynamic properties.
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a molecular theory of the homogeneous Nucleation Rate ii application to argon vapor
Journal of Chemical Physics, 1999Co-Authors: Bernard Senger, Pierre Schaaf, David S Corti, Richard K Bowles, D Pointu, J C Voegel, Howard ReissAbstract:The molecular theory of the homogeneous Nucleation Rate based on the n/v-Stillinger cluster, and developed in the preceding paper (paper I), is applied to the condensation of supersatuRated argon vapor, in a preliminary calculation of the Rate of Nucleation for a single set of conditions (temperature=85 K, pressure=2500 Torr). Free energies are obtained by means of Monte Carlo simulation. Upper and lower bounds differing by only two orders of magnitude are obtained. Since the best current measurements of vapor phase Nucleation Rates are accuRate to within about a single order of magnitude, this result is considered promising. The direction of future work to improve the accuracy of the predicted Rate is clear, and considerable improvement should be possible. These directions are discussed in the paper. Also, the essentially non ad hoc nature of the n/v-Stillinger cluster is demonstRated by the appearance of a range of connectivity distances (in a predicted location) within which the calculated Nucleation r...
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a molecular theory of the homogeneous Nucleation Rate i formulation and fundamental issues
Journal of Chemical Physics, 1999Co-Authors: Bernard Senger, Pierre Schaaf, David S Corti, Richard K Bowles, J C Voegel, Howard ReissAbstract:A molecular theory of the Rate of homogeneous vapor phase Nucleation is formulated. The ultimate goal is a theory that contains no ad hoc assumptions or arbitrary parameters having magnitudes that must be assigned in an ad hoc manner. The centerpiece of the theory is a defined cluster denoted as the n/v-Stillinger cluster, a hybrid that combines the original Stillinger cluster and the more recent n/v cluster. The Stillinger component assures that redundancy is avoided in the characterization of the cluster and the n/v component makes the Monte Carlo simulation of the free energy of the cluster relatively simple, and also allows dynamics to weight the importance of a cluster to the Nucleation Rate process. In the companion paper (paper II), dealing with the application of the theory to argon vapor, it is shown that the avoidance of redundancy is of primary importance to the non ad hoc nature of the theory. The theory provides a standard against which subtle inconsistencies in earlier theories, both molecul...
Yamina Andre - One of the best experts on this subject based on the ideXlab platform.
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influence of silicon on the Nucleation Rate of gaas nanowires on silicon substRates
Journal of Physical Chemistry C, 2018Co-Authors: Hadi Hijazi, V G Dubrovskii, G Monier, Christine Leroux, Geoffrey Avit, Agnes Trassoudaine, Catherine Bougerol, Dominique Castellucci, C Robertgoumet, Yamina AndreAbstract:Despite the unavoidable presence of silicon atoms in the catalyst alloy droplets during the vapor–liquid–solid growth of III–V nanowires on silicon substRates, it remains unknown how the Nucleation of nanowires is affected by these foreign atoms. In this work, we present the first attempt to quantify the nanowire Nucleation Rate versus the silicon concentration in the droplet. We calculate the chemical potential difference per Ga–As pair in the quaternary Au–Ga–As–Si liquid alloy droplet and in solid state, and compare it to the ternary Au–Ga–As droplet without silicon. This allows us to compute the Nucleation Rates of GaAs nanowires versus the silicon concentration under different conditions. We find that the presence of silicon in the droplet decreases the Nucleation probability of GaAs nanowires for gallium-rich droplets (with the gallium contents cGA greater than 0.6) and increases it for gold-rich droplets (cGA < 0.6). The model is used to explain our experimental data for hydride vapor phase epitaxy...
