Dipolar Order in Molecular Fluids: I. Toward an Understanding

Karlström, Gunnar; Linse, Per

doi:10.1007/s10955-011-0353-1

Cited by 3 publications

(3 citation statements)

References 15 publications

(16 reference statements)

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“…The long range of convergence of χ 0s (a) might have been anticipated given that χ 0s (a) carries a similarity with the Kirkwood factor of polar liquids, which is known to be long-ranged. 75,101 It is therefore useful to make connection to this parameter describing orientational dipolar correlations. The standard definition of the Kirkwood factor of a homogeneous solvent is given by the relation 75…”

Section: Dipolar Responsementioning

confidence: 99%

Depolarized light scattering and dielectric response of a peptide dissolved in water

Martin

Fioretto

Matyushov

2014

The Journal of Chemical Physics

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The density and orientational relaxation of bulk water can be separately studied by depolarized light scattering (DLS) and dielectric spectroscopy (DS), respectively. Here we ask the question of what are the leading collective modes responsible for polarization anisotropy relaxation (DLS) and dipole moment relaxation (DS) of solutions involving mostly hydrophobic solute-water interfaces. We study, by atomistic molecular dynamics simulations, the dynamics and structure of hydration water interfacing N-Acetyl-leucine-methylamide (NALMA) dipeptide. The DLS response of the solution is consistent with three relaxation processes: bulk water, rotations of single solutes, and collective dipole-induced-dipole polarizability of the solutes, with the time-scale of 130-200 ps. No separate DLS response of the hydration shell has been identified by our simulations. Density fluctuations of the hydration layer, which largely contribute to the response, do not produce a dynamical process distinct from bulk water. We find that the structural perturbation of the orientational distribution of hydration waters by the dipeptide solute is quite significant and propagates ∼ 3 − 5 hydration layers into the bulk. This perturbation is still below that produced by hydrated globular proteins. Despite this structural perturbation, there is little change in the orientational dynamics of the hydration layers, compared to the bulk, as probed by both single-particle orientational dynamics and collective dynamics of the dipole moment of the shells. There is a clear distinction between the perturbation of the interfacial structure by the solute-solvent interaction potential and the perturbation of the interfacial dynamics by the corresponding forces.

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Section: Dipolar Responsementioning

confidence: 99%

Depolarized light scattering and dielectric response of a peptide dissolved in water

Martin

Fioretto

Matyushov

2014

The Journal of Chemical Physics

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“…[1]); yet a deep understanding of the many-body phenomena giving rise to the collective dipolar polarization is still incomplete. Such an understanding of the relation between the molecular properties and interactions, on one hand, and the spontaneous and fluctuating polarization, on the other hand, is of central importance (i) to rationalize the solvation of ions in media and manipulate properties of solvent P. Linse ( )…”

Section: Introductionmentioning

confidence: 99%

“…In the preceding paper [1] of this issue, also referred to as paper I, we have by simulations investigated how the dipole polarization of a fluid composed of spherical particles with ideal dipole moments is affected by manipulations of the radial and of the angular spatial correlations among the particles. In the present contribution, we will examine how the polarization of a dipolar fluid is affected by its molecular properties through (i) shape deviation from spherical symmetry and (ii) deviation from a pure electrostatic dipole-dipole interaction.…”

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confidence: 99%

Dipolar Order in Molecular Fluids: II. Molecular Influence

Linse

Karlström

2011

J Stat Phys

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The influence on the short-range packing in dipolar fluids by molecular shape and by additional higher order electrostatic moments has been investigated by molecular dynamic simulations. The dipole polarization was found to decrease as the particles were elongated parallel to the dipole and to increase for elongation perpendicular to the dipole, eventually forming a nematic order. The addition of a quadrupole lead to a reduction of the polarization, and the influence of an axial octupole was weaker and more complex. Both a decrease and an increase of the polarization is possible depending on the relative dipoledipole and octupole-octupole interaction strengths and the relative direction of the symmetry axes of the moments. These observations were attributed to the different parity of a dipole and a quadrupole and the same parity of a dipole and an axial octupole under reflection. In addition, further insights into the formation of dipole polarization were obtained. Short polar and long equatorial radii and strong dipole-dipole interaction are particle properties that promote a fluid with a high dipole polarization.Keywords Dipolar order · Molecular fluid · Molecular shape · Electrostatic multipole moment IntroductionInvestigations of the dielectric behavior of molecular media have been the subject for over 150 years (see references given in Ref. [1]); yet a deep understanding of the many-body phenomena giving rise to the collective dipolar polarization is still incomplete. Such an understanding of the relation between the molecular properties and interactions, on one hand, and the spontaneous and fluctuating polarization, on the other hand, is of central importance (i) to rationalize the solvation of ions in media and manipulate properties of solvent P. Linse ( )

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MOLSIM: A modular molecular simulation software

Reščič

Linse

2015

J Comput Chem

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The modular software MOLSIM for all‐atom molecular and coarse‐grained simulations is presented with focus on the underlying concepts used. The software possesses four unique features: (1) it is an integrated software for molecular dynamic, Monte Carlo, and Brownian dynamics simulations; (2) simulated objects are constructed in a hierarchical fashion representing atoms, rigid molecules and colloids, flexible chains, hierarchical polymers, and cross‐linked networks; (3) long‐range interactions involving charges, dipoles and/or anisotropic dipole polarizabilities are handled either with the standard Ewald sum, the smooth particle mesh Ewald sum, or the reaction‐field technique; (4) statistical uncertainties are provided for all calculated observables. In addition, MOLSIM supports various statistical ensembles, and several types of simulation cells and boundary conditions are available. Intermolecular interactions comprise tabulated pairwise potentials for speed and uniformity and many‐body interactions involve anisotropic polarizabilities. Intramolecular interactions include bond, angle, and crosslink potentials. A very large set of analyses of static and dynamic properties is provided. The capability of MOLSIM can be extended by user‐providing routines controlling, for example, start conditions, intermolecular potentials, and analyses. An extensive set of case studies in the field of soft matter is presented covering colloids, polymers, and crosslinked networks. © 2015 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

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Dipolar Order in Molecular Fluids: I. Toward an Understanding

Cited by 3 publications

References 15 publications

Depolarized light scattering and dielectric response of a peptide dissolved in water

Depolarized light scattering and dielectric response of a peptide dissolved in water

Dipolar Order in Molecular Fluids: II. Molecular Influence

MOLSIM: A modular molecular simulation software

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