Self-diffusion in <i>n</i>-alkane fluid models

Padilla, P.; Toxværd, Søren

doi:10.1063/1.460475

Cited by 135 publications

(61 citation statements)

References 26 publications

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“…The united atom approximation has been shown to be able to predict the phase behavior of pure n-alkanes from C 5 up to C 48 , and the equation of state of alkanes at high or moderate densities is in good agreement with experiment [1] and [6]. This is remarkable for a model that includes a small number of adjustable parameters, namely the Lennard-Jones energy parameter and a size parameter for each united atom, and which relies on a simple (isotropic or anisotropic) united atom description of the molecules.…”

Section: Resultssupporting

confidence: 49%

“…In order to simulate alkane properties, we used the Padilla and Toxvaerd anisotropic united atom (AUA) model [1] where the united atom potential centers are displaced from the carbon atom positions. The bonds are modeled by constraining the distance between adjacent groups.…”

Section: Molecular Modelsmentioning

confidence: 99%

“…In this way groups of atoms are represented by one interaction site. For instance in linear alkanes, CH 3 and CH 2 groups are typically reduced to single sites.In order to simulate alkane properties, we used the Padilla and Toxvaerd anisotropic united atom (AUA) model [1] where the united atom potential centers are displaced from the carbon atom positions. The bonds are modeled by constraining the distance between adjacent groups.…”

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confidence: 99%

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Molecular Simulations As a Tool for Predicting Phase Equilibria and Transport Properties of Fluids

Fuchs

Boutin

Rousseau

1998

Rev. Inst. Fr. Pét.

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Dans cet article, nous passons bri•vement en revue les mŽthodes de simulation molŽculaire applicables ˆ la prŽdiction des propriŽtŽs thermophysiques des fluides et des mŽlanges. Nous montrons, d'une part, comment la mŽthode de Monte-Carlo dans l'ensemble de Gibbs permet de prŽdire le comportement de phase de fluides rŽels dans des conditions telles que l'acquisition de donnŽes expŽrimen-tales serait difficile, voire impossible. D'autre part, nous dŽcrivons les mŽthodes de dynamique molŽculaire utilisŽes pour prŽdire les propriŽtŽs de transport de fluides molŽculaires. Enfin, nous discutons le potentiel de ces mŽthodes pour les applications futures. MOLECULAR SIMULATIONS AS A TOOL FOR PREDICTING PHASE EQUILIBRIA AND TRANSPORT PROPERTIES OF FLUIDSWe briefly review the molecular simulation methods which can be used to predict thermophysical properties of fluids and fluid mixtures. It is shown in this paper, on the one hand, how the Gibbs Ensemble Monte Carlo Method allows phase behavior predictions for real fluids under conditions for which experimental data are difficult or impossible to obtain. On the other hand, the molecular dynamics methods used for predicting transport properties of molecular fluids are described. Finally we discuss possible future applications of these methods. SIMULACIONES MOLECULARES UTILIZADAS COMO HERRAMIENTAS PARA LA PREDICCIîN DES LOS EQUILIBRIOS DE FASES Y LAS PROPIEDADES DE TRANSPORTE DE LOS FLUIDOSSe examinan breve y sucesivamente, los mŽtodos de simulaci-n molecular aplicables a la predicci-n del las propiedades termof'sicas de los fluidos y de las mezclas. En este art'culo se exponen, en primer lugar, c-mo el mŽtodo de Monte Carlo en el conjunto de Gibbs permite predecir el comportamiento de fase de fluidos reales en tales condiciones que la adquisici-n de datos experimentales ser'a dif'cil, por no decir imposible. En segundo lugar, se describen los mŽtodos de din ‡mica molecular utilizados utilizados para predecir las propiedades de transporte de fluidos moleculares, Finalmente, se pone en discusi-n el potencial de estos mŽtodos para las aplicaciones futuras. Copyright © 1998, Institut français du pétrole INTRODUCTIONMolecular simulation and molecular modeling techniques are profitably employed nowadays in several industrial sectors. The use of molecular simulation includes, for instance, the design of new molecules or phases through the prediction of their physical or chemical properties. Knowledge of phase equilibria and transport properties of multicomponent gases and oils is of great economic importance in reservoir modeling, as well as in the planning of transport and in the design of industrial plants. Although the physical properties have, in general, been well studied, certain areas remain extremely difficult to access by experimentation. These include systems under high pressure and temperature as well as molecules for which pure samples may not be readily available. However, there is a great deal of interest in studying these systems precisely because of the existence o...

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Section: Resultssupporting

confidence: 49%

Section: Molecular Modelsmentioning

confidence: 99%

mentioning

confidence: 99%

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Molecular Simulations As a Tool for Predicting Phase Equilibria and Transport Properties of Fluids

Fuchs

Boutin

Rousseau

1998

Rev. Inst. Fr. Pét.

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“…For the torsion, Eq. ͑25͒ was used with the parameters proposed by Padilla and Toxvaerd, 49 namely c 0 ϭ1038 ͑K͒, c 1 ϭ2426 ͑K͒, c 2 ϭ81.6 ͑K͒, c 3 ϭϪ3129 ͑K͒, c 4 ϭϪ163 ͑K͒, and c 5 ϭϪ252 ͑K͒. The bond length was fixed to 1.539 ͑Å͒.…”

Section: The Modelmentioning

confidence: 99%

“…Toxvaerd 21,49 introduced an anisotropic potential to model the effects of hydrogen on the thermodynamic properties without increasing the number of interaction sites. In this model, the interaction site of the nonbonded LennardJones potential is displaced with respect to the center of mass of the carbon atoms ͑see Fig.…”

Section: The Modelmentioning

confidence: 99%

Computer simulations of vapor–liquid phase equilibria of n-alkanes

Smit

Karaborni

Siepmann

1995

The Journal of Chemical Physics

483

188

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For petrochemical applications knowledge of the critical properties of the n-alkanes is of interest even at temperatures where these molecules are thermally unstable. Computer simulations can determine the vapor-liquid coexistence curve of a large number of n-alkanes ranging from pentane ͑C 5 ͒ through octatetracontane ͑C 48 ͒. We have compared the predicted phase diagrams of various models with experimental data. Models which give nearly identical properties of liquid alkanes at standard conditions may have critical temperatures that differ by more than 100 K. A new n-alkane model has been developed by us that gives a good description of the phase behavior over a large temperature range. For modeling vapor-liquid coexistence a relatively simple united atom model was sufficient to obtain a very good agreement with experimental data; thus it appears not necessary to take the hydrogen atoms explicitly into account. The model developed in this work has been used to determine the critical properties of the long-chain alkanes for which experiments turned out to be difficult and contradictory. We found that for the long-chain alkanes ͑C 8 -C 48 ͒ the critical density decreases as a function of the carbon number. These simulations were made possible by the use of a recently developed simulation technique, which is a combination of the Gibbs-ensemble technique and the configurational-bias Monte Carlo method. Compared with the conventional Gibbs-ensemble technique, this method is several orders of magnitude more efficient for pentane and up to a hundred orders of magnitude for octatetracontane. This recent development makes it possible to perform routinely phase equilibrium calculations of complex molecules.

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