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  • 1
    Electronic Resource
    Electronic Resource
    Phase behavior of parallel cut spheres. Monte Carlo and integral equation results (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4551-4558 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulations of a system of 2500 parallel cut spheres of thickness L/D=0.1 give evidence for a phase transition, at packing fraction η∼0.40, from the low density nematic phase to a smectic phase. No tendency to formation of columnar ordering is observed up to densities as high as η=0.60. This behavior contrasts with that of freely rotating cut spheres for which the sequence of stable phases has been identified as isotropic–nematic–columnar–solid [D. Frenkel, Liquid Cryst. 5, 929 (1989)]. For the present system of highly anisotropic molecules the slow convergence of the expansion of correlation functions on rotational invariants precludes quantitative comparison between integral equation theory and simulation results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462790
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  • 2
    Electronic Resource
    Electronic Resource
    Nematic to smectic-A transition of parallel dipolar hard spherocylinders and ellipsoids, a hypernetted chain equation study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3197-3205 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The thermodynamic, dielectric, and structural properties of systems of dipolar hard spherocylinders and ellipsoids with perfect nematic order are investigated by means of the hypernetted chain (HNC) equation. The density, temperature domain for which the HNC equation admits a stable solution is determined. For spherocylinders a large increase of the main peak of the total structure factor in the vicinity of the stability limit of the HNC equation is, tentatively, associated with the onset of a nematic–smectic-A transition. The situation seems less clear for dipolar ellipsoids, though the results are in many aspects qualitatively similar to the spherocylinder case. The pair structure near the transition is analyzed. It is not characteristic of any of the smectic-A phase structures typical of strongly polar liquid crystals. This is probably a consequence of the highly symmetric nature of the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457870
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  • 3
    Electronic Resource
    Electronic Resource
    Integral equation study of parallel hard spherocylinders (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7403-7411 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The hypernetted chain (HNC) and Percus–Yevick (PY) integral equations are solved numerically for parallel hard spherocylinders of length-to-width ratios L/σ ranging from 0.5 to 5.0. The PY virial pressure is in excellent agreement with Monte Carlo data. The HNC equation gives evidence for the existence of a nematic to smectic-A phase transition at densities which compare reasonably well with the Monte Carlo (MC) estimates, whereas the PY equation gives stable nematic solutions for densities beyond the MC transition densities. For a given packing fraction η, pressure and pair correlation functions (properly scaled) depend very little on the elongation L/σ in the range 3–5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456220
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  • 4
    Electronic Resource
    Electronic Resource
    Density functional theory applied to the isotropic–nematic transition in model liquid crystals (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6941-6946 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The isotropic–nematic phase transition is investigated for several model liquid crystals using the density functional method. The models considered are hard ellipsoids of revolution (both prolate and oblate cases), hard spherocylinders, and two additional fluids characterized by pair potentials of a generalized Maier–Saupe type. The direct pair correlation functions for the isotropic phase are obtained by numerical solution of the hypernetted-chain (HNC) and Percus–Yevick (PY) integral equation theories. It is shown that second order density functional theory is strongly dependent upon the approximation used for the isotropic direct pair correlation function. In all cases the density functional results are qualitatively consistent with conclusions based upon orientational stability criteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455319
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  • 5
    Electronic Resource
    Electronic Resource
    Integral equation theory applied to a binary mixture under extreme conditions of density and temperature (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3096-3100 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We apply integral equation theory to the calculation of the thermodynamics and the distribution functions of a mixture of hydrogen atoms and molecules at high densities and temperatures. The integral equations are found to tackle very efficiently the problem of the softness and the nonadditivity of the potentials, as encountered under these conditions, and give better results than hard sphere perturbation theory. Comparison with Monte Carlo calculations show that the so-called HMSA and modified hypernetted chain (MHNC) equations, give almost perfect results. This extends the range of validity of these schemes to domains of high pressures and temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459832
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical properties of polarizable ionic solutions. I. Theoretical aspects (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5544-5554 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We generalize previous work [J. Chem. Phys. 85, 6645 (1986)] on the relation between the frequency-dependent dielectric constant and conductivity and time correlation functions of electrical current and polarization in electrolyte solutions by allowing the ions and solvent molecules to be polarizable. Detailed results are given for the infinite system (no boundary), spherical system embedded in a continuum and periodic boundary conditions. The Stillinger–Lovett (SL) sum rules are derived for these geometries. It is shown, in particular, that they provide a means of calculating the high frequency dielectric constant in a molecular dynamics simulation. A test of the phenomenological coefficient-susceptibility relations and the SL conditions is presented in part II by performing molecular dynamics simulations on a model electrolyte solution with different boundary conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457557
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical properties of polarizable ionic solutions. II. Computer simulation results (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5555-5566 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present molecular dynamics simulations for two limiting models of ionic solutions: one where the solvent molecules are polar, but nonpolarizable; the other where they are only polarizable (but have no permanent dipole moment). For both models, the static two-body correlation functions, the frequency-dependent dielectric constant and conductivity are calculated and the statistical uncertainty on these quantities estimated for molecular dynamics runs of the order of 105 integration steps. For the case of the polar solvent, the accuracy of the computed static interionic correlation functions allows a valuable test of the hypernetted chain integral equation theory at an ionic concentration of 0.04. The quantitative variation of the fluctuations of polarization and electrical current with change of boundary conditions is evaluated within the context of the second model (polarizable nonpolar solvent). Applying the relationships derived in Part I between the phenomenological coefficients and susceptibilities, it is shown that consistent values for the dielectric constant and electrical conductivity are obtained. The sum rules which generalize the Stillinger–Lovett conditions to ionic solutions are computed and shown to be satisfied in our simulations. The evaluation of these sum rules constitutes an important test of the convergence of the electrolyte system to an equilibrium state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457558
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  • 8
    Electronic Resource
    Electronic Resource
    Application of hard sphere perturbation theory to a high-temperature binary mixture (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7395-7402 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We calculate the thermodynamics of a high-temperature binary mixture (kT/ε〉50) using a WCA fluid perturbation theory and hard sphere reference system. The problems of the softness of the repulsive core and the nonadditivity of the hard sphere diameters can be successfully circumvented by using appropriate separations between the reference and the perturbation potentials, as shown by comparing the results with Monte Carlo simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456219
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  • 9
    Electronic Resource
    Electronic Resource
    Monte Carlo study of the thermodynamic stability of the nematic phase of a semiflexible liquid crystal model (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3820-3831 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper reports a Monte Carlo (MC) study of the ordering in a semiflexible liquid crystal model designed to give a crude representation of 4-n-octyl-4′-cyanobiphenyl (PCB). A mechanically stable nematic phase is obtained and the question of its thermodynamic stability is addressed by comparing the free energy to that of the isotropic phase. The free energies are calculated by thermodynamic integration using an efficient configuration biased MC scheme. Pair distribution functions, orientational correlation functions, and conformational properties of the nematic and isotropic phases are contrasted. In the isotropic phase the equation of state is compared with theoretical predictions for systems of convex molecules and chains made up of tangent hard spheres. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470060
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  • 10
    Electronic Resource
    Electronic Resource
    Free energy and cluster structure in the coexistence region of the restricted primitive model (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7610-7621 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The method of thermodynamic integration is used to determine the free energy of the restricted primitive model of electrolytes along two subcritical isotherms. The densities of liquid-gas coexistence derived from these data are found to be in good agreement with recent estimates from Gibbs ensemble Monte Carlo calculations. The difficulties of the free energy approach—which reside in the necessity of obtaining extremely accurate free energy values at near critical temperatures—is stressed. A detailed account is given of the clustering properties of the ions in the vapor phase, including cluster populations and energies, as well as intercluster contributions to the thermodynamic properties. The validity of several cluster theories for the free energy is investigated. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469012
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