Commentary by Hautman

Hautman, Mary Ann

doi:10.1177/0193945903252420

Cited by 2 publications

(8 citation statements)

References 3 publications

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“…We used the 3D Ewald method on the basis of U d in Eq. (11) [68][69][70][71][72] . To realize crystal, we slowly cooled the system from a liquid above the melting temperature (∼ /k B ) at density N/V = 0.84σ −3 1 .…”

Section: Simulation Methodsmentioning

confidence: 99%

“…We depict the impurities whose distance to some dipole in the PNR is shorter than 1.4. We find the numbers of the c=0.2, µ 0 =0.8 constituent dipoles and impurities as (a) (120, 70) and (b) (70,50) using the definition of PNRs in Sec.IVD. Here, the dipoles tend to be parallel to the impurity surfaces, as discussed in Sec.IVA, and almost all the impurities are on the PNR boundaries, resulting in plate-like PNRs.…”

Section: E Single Polar Nanoregion and Local Electric Fieldmentioning

confidence: 99%

“…The numerical calculations were preformed on CRAY XC40 at YITP in Kyoto University and on SGI ICE XA/UV at ISSP in the University of Tokyo. Appendix A: Electrostatics of dipole systems Here, we explain the electrostatics of dipoles between metal walls in applied field [68][69][70][71][72] . The electric potential due to the image dipoles is equivalent to that due to the surface charge densities, written as σ 0 (x, y) at z = 0 and σ H (x, y) at z = H. Without adsorption and ionization on the surfaces, the dipole centers are somewhat away from the walls (see the comment below Eq.…”

Section: Summary and Remarksmentioning

confidence: 99%

“…On the other hand, we investigate general aspects of ferroelectric glass with a simple molecular model. In electrostatics, we use an Ewald scheme includ-ing image dipoles and applied electric field 68,69 , which has been used to study water between electrodes [70][71][72] . To prepare a mixed crystal, we cool a liquid mixture from high T ; then, our impurity distribution at low T is naturally formed during crystallization 57,58 .…”

Section: Introductionmentioning

confidence: 99%

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Ferroelectric glass of spheroidal dipoles with impurities: polar nanoregions, response to applied electric field, and ergodicity breakdown

Takae

Ōnuki

2017

J. Phys.: Condens. Matter

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Using molecular dynamics simulation, we study dipolar glass in crystals composed of slightly spheroidal, polar particles and spherical, apolar impurities between metal walls. We present physical pictures of ferroelectric glass, which have been observed in relaxors, mixed crystals (such as KCN KBr ), and polymers. Our systems undergo a diffuse transition in a wide temperature range, where we visualize polar nanoregions (PNRs) surrounded by impurities. In our simulation, the impurities form clusters and their space distribution is heterogeneous. The polarization fluctuations are enhanced at relatively high T depending on the size of the dipole moment. They then form frozen PNRs as T is further lowered into the nonergodic regime. As a result, the dielectric permittivity exhibits the characteristic features of relaxor ferroelectrics. We also examine nonlinear response to cyclic applied electric field and nonergodic response to cyclic temperature changes (ZFC/FC), where the polarization and the strain change collectively and heterogeneously. We also study antiferroelectric glass arising from molecular shape asymmetry. We use an Ewald scheme of calculating the dipolar interaction in applied electric field.

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Section: Simulation Methodsmentioning

confidence: 99%

Section: E Single Polar Nanoregion and Local Electric Fieldmentioning

confidence: 99%

Section: Summary and Remarksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ferroelectric glass of spheroidal dipoles with impurities: polar nanoregions, response to applied electric field, and ergodicity breakdown

Takae

Ōnuki

2017

J. Phys.: Condens. Matter

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“…Generally, the electric potential can change noticeably across a microscopic Stern layer at a solid-water interface 1-3, 40 . We mention molecular dynamics simulations on this effect [41][42][43][44][45] . In our case, there are two such layers at the bottom and top.…”

Section: B Electric Potential and Stern Layersmentioning

confidence: 99%

Ionization at a solid-water interface in an applied electric field: Charge regulation

Okamoto

Ōnuki

2016

The Journal of Chemical Physics

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We investigate ionization at a solid-water interface in an applied electric field. We attach an electrode to a dielectric film bearing silanol or carboxyl groups with an areal density Γ, where the degree of dissociation α is determined by the proton density in water close to the film. We show how α depends on the density n of NaOH in water and the surface charge density σ on the electrode. For σ > 0, the protons are expelled away from the film, leading to an increase in α. In particular, in the range 0 < σ < eΓ, self-regulation occurs to realize α ≅ σ/eΓ for n ≪ n, where n is 0.01 mol/L for silica surfaces and is 2 × 10 mol/L for carboxyl-bearing surfaces. We also examine the charge regulation with decreasing the cell thickness H below the Debye length κ, where a crossover occurs at the Gouy-Chapman length. In particular, when σ ∼ eΓ and H ≪ κ, the surface charges remain only partially screened by ions, leading to a nonvanishing electric field in the interior.

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Commentary by Hautman

Cited by 2 publications

References 3 publications

Ferroelectric glass of spheroidal dipoles with impurities: polar nanoregions, response to applied electric field, and ergodicity breakdown

Ferroelectric glass of spheroidal dipoles with impurities: polar nanoregions, response to applied electric field, and ergodicity breakdown

Ionization at a solid-water interface in an applied electric field: Charge regulation

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