An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility.
Identifieur interne : 001174 ( Ncbi/Merge ); précédent : 001173; suivant : 001175An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility.
Auteurs : Thijs Van Westen [Pays-Bas] ; Bernardo Oyarzún [Pays-Bas] ; Thijs J H. Vlugt [Pays-Bas] ; Joachim Gross [Allemagne]Source :
- The Journal of chemical physics [ 1089-7690 ] ; 2015.
Abstract
We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to be fully flexible, partially flexible (rod-coil), or rigid linear. The hard-chain reference contribution to the EoS is obtained from a Vega-Lago rescaled Onsager theory. For the description of the (attractive) dispersion interactions between molecules, we adopt a segment-segment approach. We show that the perturbation contribution for describing these interactions can be divided into an "isotropic" part, which depends only implicitly on orientational ordering of molecules (through density), and an "anisotropic" part, for which an explicit dependence on orientational ordering is included (through an expansion in the nematic order parameter). The perturbation theory is used to study the effect of chain length, molecular flexibility, and attractive interactions on IN phase equilibria of pure LJ chain fluids. Theoretical results for the IN phase equilibrium of rigid linear LJ 10-mers are compared to results obtained from Monte Carlo simulations in the isobaric-isothermal (NPT) ensemble, and an expanded formulation of the Gibbs-ensemble. Our results show that the anisotropic contribution to the dispersion attractions is irrelevant for LJ chain fluids. Using the isotropic (density-dependent) contribution only (i.e., using a zeroth order expansion of the attractive Helmholtz energy contribution in the nematic order parameter), excellent agreement between theory and simulations is observed. These results suggest that an EoS contribution for describing the attractive part of the dispersion interactions in real LCs can be obtained from conventional theoretical approaches designed for isotropic fluids, such as a Perturbed-Chain Statistical Associating Fluid Theory approach.
DOI: 10.1063/1.4922921
PubMed: 26133453
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Vlugt</name><affiliation wicri:level="1"><nlm:affiliation>Process & Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.</nlm:affiliation><country xml:lang="fr">Pays-Bas</country><wicri:regionArea>Process & Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft</wicri:regionArea><wicri:noRegion>2628 CB Delft</wicri:noRegion></affiliation></author><author><name sortKey="Gross, Joachim" sort="Gross, Joachim" uniqKey="Gross J" first="Joachim" last="Gross">Joachim Gross</name><affiliation wicri:level="3"><nlm:affiliation>Institut für Thermodynamik und Thermische Verfahrenstechnik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany.</nlm:affiliation><country xml:lang="fr">Allemagne</country><wicri:regionArea>Institut für Thermodynamik und Thermische Verfahrenstechnik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart</wicri:regionArea><placeName><region type="land" nuts="1">Bade-Wurtemberg</region><region type="district" nuts="2">District de Stuttgart</region><settlement type="city">Stuttgart</settlement></placeName></affiliation></author></analytic><series><title level="j">The Journal of chemical physics</title><idno type="eISSN">1089-7690</idno><imprint><date when="2015" type="published">2015</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to be fully flexible, partially flexible (rod-coil), or rigid linear. The hard-chain reference contribution to the EoS is obtained from a Vega-Lago rescaled Onsager theory. For the description of the (attractive) dispersion interactions between molecules, we adopt a segment-segment approach. We show that the perturbation contribution for describing these interactions can be divided into an "isotropic" part, which depends only implicitly on orientational ordering of molecules (through density), and an "anisotropic" part, for which an explicit dependence on orientational ordering is included (through an expansion in the nematic order parameter). The perturbation theory is used to study the effect of chain length, molecular flexibility, and attractive interactions on IN phase equilibria of pure LJ chain fluids. Theoretical results for the IN phase equilibrium of rigid linear LJ 10-mers are compared to results obtained from Monte Carlo simulations in the isobaric-isothermal (NPT) ensemble, and an expanded formulation of the Gibbs-ensemble. Our results show that the anisotropic contribution to the dispersion attractions is irrelevant for LJ chain fluids. Using the isotropic (density-dependent) contribution only (i.e., using a zeroth order expansion of the attractive Helmholtz energy contribution in the nematic order parameter), excellent agreement between theory and simulations is observed. These results suggest that an EoS contribution for describing the attractive part of the dispersion interactions in real LCs can be obtained from conventional theoretical approaches designed for isotropic fluids, such as a Perturbed-Chain Statistical Associating Fluid Theory approach. </div></front></TEI><pubmed><MedlineCitation Status="PubMed-not-MEDLINE" Owner="NLM"><PMID Version="1">26133453</PMID><DateCompleted><Year>2015</Year><Month>09</Month><Day>25</Day></DateCompleted><DateRevised><Year>2015</Year><Month>07</Month><Day>03</Day></DateRevised><Article PubModel="Print"><Journal><ISSN IssnType="Electronic">1089-7690</ISSN><JournalIssue CitedMedium="Internet"><Volume>142</Volume><Issue>24</Issue><PubDate><Year>2015</Year><Month>Jun</Month><Day>28</Day></PubDate></JournalIssue><Title>The Journal of chemical physics</Title><ISOAbbreviation>J Chem Phys</ISOAbbreviation></Journal><ArticleTitle>An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility.</ArticleTitle><Pagination><MedlinePgn>244903</MedlinePgn></Pagination><ELocationID EIdType="doi" ValidYN="Y">10.1063/1.4922921</ELocationID><Abstract><AbstractText>We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to be fully flexible, partially flexible (rod-coil), or rigid linear. The hard-chain reference contribution to the EoS is obtained from a Vega-Lago rescaled Onsager theory. For the description of the (attractive) dispersion interactions between molecules, we adopt a segment-segment approach. We show that the perturbation contribution for describing these interactions can be divided into an "isotropic" part, which depends only implicitly on orientational ordering of molecules (through density), and an "anisotropic" part, for which an explicit dependence on orientational ordering is included (through an expansion in the nematic order parameter). The perturbation theory is used to study the effect of chain length, molecular flexibility, and attractive interactions on IN phase equilibria of pure LJ chain fluids. Theoretical results for the IN phase equilibrium of rigid linear LJ 10-mers are compared to results obtained from Monte Carlo simulations in the isobaric-isothermal (NPT) ensemble, and an expanded formulation of the Gibbs-ensemble. Our results show that the anisotropic contribution to the dispersion attractions is irrelevant for LJ chain fluids. Using the isotropic (density-dependent) contribution only (i.e., using a zeroth order expansion of the attractive Helmholtz energy contribution in the nematic order parameter), excellent agreement between theory and simulations is observed. These results suggest that an EoS contribution for describing the attractive part of the dispersion interactions in real LCs can be obtained from conventional theoretical approaches designed for isotropic fluids, such as a Perturbed-Chain Statistical Associating Fluid Theory approach. </AbstractText></Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>van Westen</LastName><ForeName>Thijs</ForeName><Initials>T</Initials><AffiliationInfo><Affiliation>Process & Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Oyarzún</LastName><ForeName>Bernardo</ForeName><Initials>B</Initials><AffiliationInfo><Affiliation>Process & Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Vlugt</LastName><ForeName>Thijs J H</ForeName><Initials>TJ</Initials><AffiliationInfo><Affiliation>Process & Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Gross</LastName><ForeName>Joachim</ForeName><Initials>J</Initials><AffiliationInfo><Affiliation>Institut für Thermodynamik und Thermische Verfahrenstechnik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany.</Affiliation></AffiliationInfo></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D016428">Journal Article</PublicationType></PublicationTypeList></Article><MedlineJournalInfo><Country>United States</Country><MedlineTA>J Chem Phys</MedlineTA><NlmUniqueID>0375360</NlmUniqueID><ISSNLinking>0021-9606</ISSNLinking></MedlineJournalInfo></MedlineCitation><PubmedData><History><PubMedPubDate PubStatus="entrez"><Year>2015</Year><Month>7</Month><Day>3</Day><Hour>6</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="pubmed"><Year>2015</Year><Month>7</Month><Day>3</Day><Hour>6</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="medline"><Year>2015</Year><Month>7</Month><Day>3</Day><Hour>6</Hour><Minute>1</Minute></PubMedPubDate></History><PublicationStatus>ppublish</PublicationStatus><ArticleIdList><ArticleId IdType="pubmed">26133453</ArticleId><ArticleId IdType="doi">10.1063/1.4922921</ArticleId></ArticleIdList></PubmedData></pubmed><affiliations><list><country><li>Allemagne</li><li>Pays-Bas</li></country><region><li>Bade-Wurtemberg</li><li>District de Stuttgart</li></region><settlement><li>Stuttgart</li></settlement></list><tree><country name="Pays-Bas"><noRegion><name sortKey="Van Westen, Thijs" sort="Van Westen, Thijs" uniqKey="Van Westen T" first="Thijs" last="Van Westen">Thijs Van Westen</name></noRegion><name sortKey="Oyarzun, Bernardo" sort="Oyarzun, Bernardo" uniqKey="Oyarzun B" first="Bernardo" last="Oyarzún">Bernardo Oyarzún</name><name sortKey="Vlugt, Thijs J H" sort="Vlugt, Thijs J H" uniqKey="Vlugt T" first="Thijs J H" last="Vlugt">Thijs J H. Vlugt</name></country><country name="Allemagne"><region name="Bade-Wurtemberg"><name sortKey="Gross, Joachim" sort="Gross, Joachim" uniqKey="Gross J" first="Joachim" last="Gross">Joachim Gross</name></region></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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