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Venkatareddy N, Lin ST, Maiti PK. Phase behavior of active and passive dumbbells. Phys Rev E 2023; 107:034607. [PMID: 37073042 DOI: 10.1103/physreve.107.034607] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 03/08/2023] [Indexed: 04/20/2023]
Abstract
We report phase separation in a mixture of "hot" and "cold" three-dimensional dumbbells which interact by Lennard-Jones potential. We also have studied the effect of asymmetry of dumbbells and the variation of ratio of "hot" and "cold" dumbbells on their phase separation. The ratio of the temperature difference between hot and cold dumbbells to the temperature of cold dumbbells is a measure of the activity χ of the system. From constant density simulations of symmetric dumbbells, we observe that the "hot" and "cold" dumbbells phase separate at higher activity ratio (χ>5.80) compared to that of a mixture of hot and cold Lennard-Jones monomers (χ>3.44). We find that, in the phase-separated system, the hot dumbbells have high effective volume and hence high entropy which is calculated by two-phase thermodynamic method. The high kinetic pressure of hot dumbbells forces the cold dumbbells to form dense clusters such that at the interface the high kinetic pressure of hot dumbbells is balanced by the virial pressure of cold dumbbells. We find that phase separation pushes the cluster of cold dumbbells to have solidlike ordering. Bond orientation order parameters reveal that the cold dumbbells form solidlike ordering consisting of predominantly face-centered cubic and hexagonal-close packing packing, but the individual dumbbells have random orientations. The simulation of the nonequilibrium system of symmetric dumbbells at different ratios of number of hot dumbbells to cold dumbbells reveals that the critical activity of phase separation decreases with increase in fraction of hot dumbbells. The simulation of equal mixture of hot and cold asymmetric dumbbells revealed that the critical activity of phase separation was independent of the asymmetry of dumbbells. We also observed that the clusters of cold asymmetric dumbbells showed both crystalline and noncrystalline order depending on the asymmetry of dumbbells.
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Affiliation(s)
- Nayana Venkatareddy
- Department of Physics, Indian Institute of Science, C. V. Raman Ave,Bengaluru 560012, India
| | - Shiang-Tai Lin
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 10617
| | - Prabal K Maiti
- Department of Physics, Indian Institute of Science, C. V. Raman Ave,Bengaluru 560012, India
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2
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Alkhatib III, Pereira LMC, Torne J, Vega LF. Polar soft-SAFT: theory and comparison with molecular simulations and experimental data of pure polar fluids. Phys Chem Chem Phys 2020; 22:13171-13191. [DOI: 10.1039/d0cp00846j] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The consideration of polar interactions is of vital importance for the development of predictive and accurate thermodynamic models for polar fluids, as they govern most of their thermodynamic properties, making them highly non-ideal fluids.
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Affiliation(s)
- Ismail I. I. Alkhatib
- Chemical Engineering Department
- Khalifa University of Science and Technology
- Abu Dhabi
- United Arab Emirates
- Research and Innovation Center on CO2 and H2 (RICH)
| | - Luís M. C. Pereira
- Chemical Engineering Department
- Khalifa University of Science and Technology
- Abu Dhabi
- United Arab Emirates
| | - Jordi Torne
- Alya Technology & Innovation SL
- 08202 Sabadell
- Spain
| | - Lourdes F. Vega
- Chemical Engineering Department
- Khalifa University of Science and Technology
- Abu Dhabi
- United Arab Emirates
- Research and Innovation Center on CO2 and H2 (RICH)
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3
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Eskandari Nasrabad A, Laghaei R. Thermodynamic and transport properties of nitrogen fluid: Molecular theory and computer simulations. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.03.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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4
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Mirzaeinia A, Feyzi F, Hashemianzadeh SM. Equations of state for the fully flexible WCA chains in the fluid and solid phases based on Wertheims-TPT2. J Chem Phys 2018; 148:104502. [PMID: 29544293 DOI: 10.1063/1.5018789] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Based on Wertheim's second order thermodynamic perturbation theory (TPT2), equations of state (EOSs) are presented for the fluid and solid phases of tangent, freely jointed spheres. It is considered that the spheres interact with each other through the Weeks-Chandler-Anderson (WCA) potential. The developed TPT2 EOS is the sum of a monomeric reference term and a perturbation contribution due to bonding. MC NVT simulations are performed to determine the structural properties of the reference system in the reduced temperature range of 0.6 ≤ T* ≤ 4.0 and the packing fraction range of 0.1 ≤ η ≤ 0.72. Mathematical functions are fitted to the simulation results of the reference system and employed in the framework of Wertheim's theory to develop TPT2 EOSs for the fluid and solid phases. The extended EOSs are compared to the MC NPT simulation results of the compressibility factor and internal energy of the fully flexible chain systems. Simulations are performed for the WCA chain system for chain lengths of up to 15 at T* = 1.0, 1.5, 2.0, 3.0. Across all the reduced temperatures, the agreement between the results of the TPT2 EOS and MC simulations is remarkable. Overall Average Absolute Relative Percent Deviation at T* = 1.0 for the compressibility factor in the entire chain lengths we covered is 0.51 and 0.77 for the solid and fluid phases, respectively. Similar features are observed in the case of residual internal energy.
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Affiliation(s)
- Ali Mirzaeinia
- Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran
| | - Farzaneh Feyzi
- Thermodynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, Tehran 16846-13114, Iran
| | - Seyed Majid Hashemianzadeh
- Molecular Simulation Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114, Iran
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5
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Lee S, Kim M, Chang J. Chemical potential and solid-solid equilibrium of near-spherical Lennard-Jones dumbbell crystal. KOREAN J CHEM ENG 2015. [DOI: 10.1007/s11814-015-0163-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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6
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van Westen T, Vlugt TJH, Gross J. On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility. J Chem Phys 2015; 142:224504. [DOI: 10.1063/1.4922264] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Thijs van Westen
- Process and Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands
| | - Thijs J. H. Vlugt
- Process and Energy Laboratory, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands
| | - Joachim Gross
- Institut für Thermodynamik und Thermische Verfahrenstechnik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany
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7
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Gámez F. Thermodynamic of fluids from a general equation of state: The molecular discrete perturbation theory. J Chem Phys 2014; 140:234504. [DOI: 10.1063/1.4882897] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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8
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Daub CD, Åstrand PO, Bresme F. Thermo-molecular orientation effects in fluids of dipolar dumbbells. Phys Chem Chem Phys 2014; 16:22097-106. [DOI: 10.1039/c4cp03511a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Plots of first-order (left) and novel second-order (right) thermomolecular orientation effects in fluids of dipolar dumbbells.
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Affiliation(s)
- Christopher D. Daub
- Department of Chemistry
- Norwegian University of Science and Technology (NTNU)
- Trondheim, Norway
| | - Per-Olof Åstrand
- Department of Chemistry
- Norwegian University of Science and Technology (NTNU)
- Trondheim, Norway
| | - Fernando Bresme
- Department of Chemistry
- Chemical Physics Section
- Imperial College London
- London, UK
- Department of Chemistry
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Lafitte T, Apostolakou A, Avendaño C, Galindo A, Adjiman CS, Müller EA, Jackson G. Accurate statistical associating fluid theory for chain molecules formed from Mie segments. J Chem Phys 2013; 139:154504. [DOI: 10.1063/1.4819786] [Citation(s) in RCA: 304] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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10
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Galliero G. Surface tension of short flexible Lennard-Jones chains: Corresponding states behavior. J Chem Phys 2010; 133:074705. [DOI: 10.1063/1.3469860] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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11
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Barros de Oliveira A, Neves EB, Gavazzoni C, Paukowski JZ, Netz PA, Barbosa MC. Liquid crystal phase and waterlike anomalies in a core-softened shoulder-dumbbells system. J Chem Phys 2010; 132:164505. [DOI: 10.1063/1.3386384] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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SANZ E, McBRIDE C, VEGA C. The properties of fully flexible Lennard-Jones chains in the solid phase: Wertheim theory and simulation. Mol Phys 2009. [DOI: 10.1080/0026897031000112424] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- E. SANZ
- a Departamento de Química Física, Facultad de Ciencias Químicas , Universidad Complutense de Madrid, Ciudad Universitaria , 28040 , Madrid , Spain
| | - C. McBRIDE
- a Departamento de Química Física, Facultad de Ciencias Químicas , Universidad Complutense de Madrid, Ciudad Universitaria , 28040 , Madrid , Spain
| | - C. VEGA
- a Departamento de Química Física, Facultad de Ciencias Químicas , Universidad Complutense de Madrid, Ciudad Universitaria , 28040 , Madrid , Spain
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Braun H, Hentschke R. Tracking gas-liquid coexistence in fluids of charged soft dumbbells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:041501. [PMID: 19905310 DOI: 10.1103/physreve.80.041501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 08/27/2009] [Indexed: 05/28/2023]
Abstract
The existence of gas-liquid coexistence in dipolar fluids with no other contribution to attractive interaction than dipole-dipole interaction is a basic and open question in the theory of fluids. Recent Monte Carlo work by Camp and co-workers indicates that a fluid of charged hard dumbbells does exhibit gas-liquid (g-l) coexistence. This system has the potential to answer the above fundamental question because the charge-to-charge separation, d , on the dumbbells may be reduced to, at least in principle, yield the dipolar fluid limit. Using the molecular-dynamics technique we present simulation results for the g-l critical point of charged soft dumbbells at fixed dipole moment as function of d . We do find a g-l critical point at finite temperature even at the smallest d value (10;{-4}) . Reversible aggregation appears to play less a role than in related model systems as d becomes small. Consequently attempts to interpret the simulation results using either an extension of Flory's lattice theory for polymer systems, which includes reversible assembly of monomers into chains, or the defect model for reversible networks proposed by Tlusty and Safran are not successful. The overall best qualitative interpretation of the critical parameters is obtained by considering the dumbbells as dipoles immersed in a continuum dielectric.
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Affiliation(s)
- Heiko Braun
- Fachbereich Mathematik und Naturwissenschaften, Bergische Universität, D-42097 Wuppertal, Germany
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14
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Blas FJ, MacDowell LG, de Miguel E, Jackson G. Vapor-liquid interfacial properties of fully flexible Lennard-Jones chains. J Chem Phys 2009; 129:144703. [PMID: 19045161 DOI: 10.1063/1.2989115] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We consider the computation of the interfacial properties of molecular chains from direct simulation of the vapor-liquid interface. The molecules are modeled as fully flexible chains formed from tangentially bonded monomers with truncated Lennard-Jones interactions. Four different model systems comprising of 4, 8, 12, and 16 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test area and the wandering interface methods. In addition to the surface tension, we also obtain density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The interfacial thickness and surface tension appear to exhibit an asymptotic limiting behavior for long chains. A similar behavior is also observed for the coexistence densities and critical properties. Our simulation results indicate that the asymptotic regime is reached for Lennard-Jones chains formed from eight monomer segments. We also include a preliminary study on the effect of the cutoff distance on the interfacial properties. Our results indicate that all of the properties exhibit a dependence with the distance at which the interactions are truncated, though the relative effect varies from one property to the other. The interfacial thickness and, more particularly, the interfacial tension are found to be strongly dependent on the particular choice of cutoff, whereas the density profiles and coexistence densities are, in general, less sensitive to the truncation.
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Affiliation(s)
- Felipe J Blas
- Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva, Spain.
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15
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Nasrabad AE. Self-diffusion coefficient of two-center Lennard-Jones fluids: Molecular simulations and free volume theory. J Chem Phys 2009; 130:024503. [DOI: 10.1063/1.3054139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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16
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Bourov GK, Bhattacharya A. Effect of packing parameter on phase diagram of amphiphiles: An off-lattice Gibbs ensemble approach. J Chem Phys 2007; 127:244905. [DOI: 10.1063/1.2807240] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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17
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Li T, Nies E. Coarse-Grained Molecular Dynamics Modeling of Strongly Associating Fluids: Thermodynamics, Liquid Structure, and Dynamics of Symmetric Binary Mixture Fluids. J Phys Chem B 2007; 111:8131-44. [PMID: 17585801 DOI: 10.1021/jp0722096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Symmetric binary mixtures capable of strong association via a highly directional and saturable specific interaction between unlike molecules are investigated by canonical molecular dynamics simulations. The specific interaction of the molecules is defined in a new coarse-grained pair potential that can be applied in continuous molecular dynamics as well as in Monte Carlo simulations. The thermodynamic, structural, and dynamic properties of the associating mixture fluids are investigated as a function of density, temperature, and association strength of the specific interaction. Detailed analysis of the simulation data confirms a two-stage mechanism in the formation of specific bonds with increasing interaction strength, including a fast dimerization process and a subsequent stage of perfecting the bonds. A large heat capacity peak is found during the formation or breaking of the bonds, reflecting the large energy fluctuation introduced by the strong association. The fractions of nonbonded molecules obtained from the simulations as a function of density, temperature, and interaction strength are in excellent agreement with the predictions of Wertheim's thermodynamic perturbation theory. The translational and rotational dynamics of the Tmer mixture are effectively retarded with increasing association strength and are analyzed in terms of autocorrelation functions and a non-Gaussian parameter for the translational dynamics. The lifetimes of molecules in bonded and nonbonded states provide detailed information about the transformation of molecules between the bonded state and the nonbonded state. Finally, simulation sampling problems inherent to strongly interacting systems are easily overcome using the parallel tempering simulation technique. This latter result confirms that with the new continuous coarse-grained simulation potential we have a versatile and flexible interaction potential that can be used with many available molecular dynamics and Monte Carlo algorithms under various ensembles.
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Affiliation(s)
- Ting Li
- Polymer Research Division, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium.
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18
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Abstract
A perturbed chain equation of state for the solid phase has been derived. Although the equation is general with respect to intermolecular potential, we incorporate the Lennard-Jones potential in this work in order to compare results from the model with available Monte Carlo simulation data. Two forms of the radial distribution function for the hard-sphere solid chain reference state are used in the model. First, a theoretically rigorous approach is taken by using a correlation of actual solid-phase Monte Carlo hard-sphere chain data for the radial distribution function. This results in good agreement with the Monte Carlo data only at high density. Second, a simple extended-density approximation was used for the radial distribution function. This second approach was found to work well across the entire density range including the vicinity of the solid-fluid equilibrium.
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Affiliation(s)
- T W Cochran
- Department of Chemical and Biochemical Engineering, Rutgers University, Piscataway, New Jersey 08854, USA.
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19
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Paricaud P. A general perturbation approach for equation of state development: Applications to simple fluids, ab initio potentials, and fullerenes. J Chem Phys 2006; 124:154505. [PMID: 16674240 DOI: 10.1063/1.2181979] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A new perturbation scheme based on the Barker-Henderson perturbation theory [J. Chem. Phys. 47, 4714 (1967)] is proposed to predict the thermodynamic properties of spherical molecules. Accurate predictions of second virial coefficients and vapor-liquid coexistence properties are obtained for a large variety of potential functions (square well, Yukawa, Sutherland, Lennard-Jones, Buckingham, Girifalco). New Gibbs ensemble Monte Carlo simulations of the generalized exp-m Buckingham potential are reported. An extension of the perturbation approach to mixtures is proposed, and excellent predictions of vapor-liquid equilibria are obtained for Lennard-Jones mixtures. The perturbation scheme can be applied to complex potential functions fitted to ab initio data to predict the properties of real molecules such as neon. The new approach can also be used as an auxiliary tool in molecular simulation studies, to efficiently optimize an intermolecular potential on macroscopic properties or match force fields based on different potential functions.
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Affiliation(s)
- Patrice Paricaud
- Laboratoire Chimie et Procédé, UCP-ENSTA, 32 Boulevard Victor, 75739 Paris, France.
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Cochran TW, Chiew YC. Radial distribution function of freely jointed hard-sphere chains in the solid phase. J Chem Phys 2006; 124:74901. [PMID: 16497076 DOI: 10.1063/1.2167644] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Monte Carlo simulation is used to generate the radial distribution function of freely jointed tangent-bonded hard-sphere chains in the disordered solid phase for chain lengths of three, four, six, and eight segments. The data are used to create an accurate analytical expression of the total radial distribution function of the hard-sphere chains that covers a density range from the solidification point up to a packing fraction of 0.71. It is envisioned that the correlation will help further progress toward molecular thermodynamic treatment of the solid phase in general and toward perturbed chain theories for the solid phase, in particular.
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Affiliation(s)
- T W Cochran
- Department of Chemical and Biochemical Engineering, Rutgers University, Piscataway, New Jersey 08854, USA.
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21
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Llovell F, Pàmies JC, Vega LF. Thermodynamic properties of Lennard-Jones chain molecules: Renormalization-group corrections to a modified statistical associating fluid theory. J Chem Phys 2004; 121:10715-24. [PMID: 15549957 DOI: 10.1063/1.1809112] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A modified version of the statistical associating fluid theory (SAFT), the so-called soft-SAFT equation of state (EOS), has been extended by a crossover treatment to take into account the long density fluctuations encountered when the critical region is approached. The procedure, based on White's work from the renormalization group theory [Fluid Phase Equilibria 75, 53 (1992); L. W. Salvino and J. A. White, J. Chem. Phys. 96, 4559 (1992)], is implemented in terms of recursion relations where the density fluctuations are successively incorporated. The crossover soft-SAFT equation provides the correct nonclassical critical exponents when approaching the critical point, and reduces to the original soft-SAFT equation far from the critical region. The accuracy of the global equation is tested by direct comparison with molecular simulation results of Lennard-Jones chains, obtaining very good agreement and clear improvements compared to the original soft-SAFT EOS. Excellent agreement with vapor-liquid equilibrium experimental data inside and outside the critical region for the n-alkane series is also obtained. We provide a set of transferable molecular parameters for this family, unique for the whole range of thermodynamic properties.
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Affiliation(s)
- Fèlix Llovell
- Institut de Ciència de Materials de Barcelona, (ICMAB-CSIC), Consejo Superior de Investigaciones Científicas, Campus de la UAB, Bellaterra, 08193 Barcelona, Spain
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Paricaud P, Galindo A, Jackson G. Modeling the Cloud Curves and the Solubility of Gases in Amorphous and Semicrystalline Polyethylene with the SAFT-VR Approach and Flory Theory of Crystallization. Ind Eng Chem Res 2004. [DOI: 10.1021/ie049592a] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Norman G, Stegailov V. Simulation of Ideal Crystal Superheating and Decay. MOLECULAR SIMULATION 2004. [DOI: 10.1080/0892702042000197667] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Galindo A, Vega C, Sanz E, MacDowell LG, de Miguel E, Blas FJ. Computer simulation study of the global phase behavior of linear rigid Lennard-Jones chain molecules: Comparison with flexible models. J Chem Phys 2004; 120:3957-68. [PMID: 15268561 DOI: 10.1063/1.1642603] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The global phase behavior (i.e., vapor-liquid and fluid-solid equilibria) of rigid linear Lennard-Jones (LJ) chain molecules is studied. The phase diagrams for three-center and five-center rigid model molecules are obtained by computer simulation. The segment-segment bond lengths are L = sigma, so that models of tangent monomers are considered in this study. The vapor-liquid equilibrium conditions are obtained using the Gibbs ensemble Monte Carlo method and by performing isobaric-isothermal NPT calculations at zero pressure. The phase envelopes and critical conditions are compared with those of flexible LJ molecules of tangent segments. An increase in the critical temperature of linear rigid chains with respect to their flexible counterparts is observed. In the limit of infinitely long chains the critical temperature of linear rigid LJ chains of tangent segments seems to be higher than that of flexible LJ chains. The solid-fluid equilibrium is obtained by Gibbs-Duhem integration, and by performing NPT simulations at zero pressure. A stabilization of the solid phase, an increase in the triple-point temperature, and a widening of the transition region are observed for linear rigid chains when compared to flexible chains with the same number of segments. The triple-point temperature of linear rigid LJ chains increases dramatically with chain length. The results of this work suggest that the fluid-vapor transition could be metastable with respect to the fluid-solid transition for chains with more than six LJ monomer units.
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Affiliation(s)
- A Galindo
- Department of Chemical Engineering and Chemical Technology, Imperial College London, South Kensington Campus SW7 2AZ, UK.
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25
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Blas FJ, Sanz E, Vega C, Galindo A. Fluid–solid equilibria of flexible and linear rigid tangent chains from Wertheim’s thermodynamic perturbation theory. J Chem Phys 2003. [DOI: 10.1063/1.1619936] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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