The dielectric constant of polar fluids and the distribution of the total dipole moment

The treatment of the long-range dipolar interactions in simulations of mesogens is examined. After a brief reformulation of the standard Ewald summation and reaction-® eld methods in the general context of electrostatics using Green functions, we report the results of Monte Carlo simulations of liquid crystalline phases for L /D = 5 hard spherocylinders (cylinder length L and diameter D) with central point dipoles oriented along the main axis of the cylinder. In the case of N = 1020 particles an equivalent description of the thermodynamic properties and the structure of the phases is obtained with both techniques. A good description of the dielectric constant of the surrounding continuum is achieved by using a simple selfconsistent iterative method based on the calculation of the dielectric constant within the cell. The reaction-® eld method allows a systematic study of the phase behaviour of the system to be made with relatively modest computational requirements. We make a preliminary assessment of the phase behaviour for this system. In the case of molecules with central longitudinal dipoles, the nematic phase is destabilized relative to the isotropic (I) and the smectic-A (SmA) phases when compared with the non-polar system; the nematic (N) phase disappears altogether when the temperature is lowered below an I± N± SmA triple point. Furthermore, there is no evidence of ferroelectricity although some short-range antiferroelectric ordering is seen. The destabilization of the nematic phase relative to the smectic phase is also seen for systems with central transverse dipoles, but contrasts with that for molecules with terminal longitudinal dipoles where the smectic-A phase is destabilized.

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“…This procedure is equally valid for both the ES and RF methods [16,29]. According to equation (39) the value of e depends on the value of e s .…”

Section: A Self-consistent Methods For E Smentioning

confidence: 98%

Reaction-field and Ewald summation methods in Monte Carlo simulations of dipolar liquid crystals

GIL-VILLEGAS¹,

JACKSON²

1997

Molecular Physics

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“…An alternative, less computationally intensive, route to the static dielectric constant was proposed by Kusalik and Svishchev. 34 The method may be employed in future work. The static dielectric constant was calculated for both Polarflex models and compared to the literature value for the SPC/F water model.…”

Section: Resultsmentioning

confidence: 99%

A Multistate Empirical Valence Bond Approach to a Polarizable and Flexible Water Model

2001

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A new polarizable and flexible water potential has been developed based on the multistate empirical valence bond (MS-EVB) method. The model adds a charge-determination step to the simple point charge/flexible (SPC/F) potential. Two models have been developed: one that is polarizable only along the principal axis, and another that is polarizable in both directions within the molecular plane. The two models give nearly identical radial distribution functions (RDF) for the three site-site RDFs in water: oxygen-oxygen, oxygenhydrogen, and hydrogen-hydrogen. The new model exhibits a liquid structure that is more ordered than SPC/F but is still well matched to experiment. The gas-phase monomer and dimer properties of the polarizable models are much closer to the experimental result than is SPC/F. Experimental condensed phase properties, such as the bond angle, bond length, molecular dipole moment, and total energy, are also reasonably well reproduced. The static dielectric constant and self-diffusion constant of the model with two directions of polarizability are also reasonably accurate. The MS-EVB method is shown to provide a simple approach to including both polarizability and bond flexibility into a water potential.

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“…[6][7][8][9][10][11][12][13] Second, dielectric properties of the SM fluids have been reported. [14][15][16][17][18] Third, the SM/LJ binary fluids can be used to study mixtures of polar and nonpolar fluids. [19][20][21] Fourth, SM clusters can be used to study the effect of dipole strength on structures of polar clusters.…”

Section: Introductionmentioning

confidence: 99%

Freezing point and solid-liquid interfacial free energy of Stockmayer dipolar fluids: A molecular dynamics simulation study

Wang

Apte

Morris

et al. 2013

The Journal of Chemical Physics

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Stockmayer fluids are a prototype model system for dipolar fluids. We have computed the freezing temperatures of Stockmayer fluids at zero pressure using three different molecular-dynamics simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature two-phase coexistence method, and the constant-pressure and constant-enthalpy two-phase coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with the dimensionless dipole moment μ*=1, √2, √3 is 0.656 ± 0.001, 0.726 ± 0.002, and 0.835 ± 0.005, respectively. The freezing temperature increases with the dipolar strength. Moreover, for the first time, the solid-liquid interfacial free energies γ of the fcc (111), (110), and (100) interfaces are computed using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, i.e., γ100 > γ110 > γ111.

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The dielectric constant of polar fluids and the distribution of the total dipole moment

Cited by 43 publications

References 28 publications

Reaction-field and Ewald summation methods in Monte Carlo simulations of dipolar liquid crystals

Reaction-field and Ewald summation methods in Monte Carlo simulations of dipolar liquid crystals

A Multistate Empirical Valence Bond Approach to a Polarizable and Flexible Water Model

Freezing point and solid-liquid interfacial free energy of Stockmayer dipolar fluids: A molecular dynamics simulation study

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