Using Atomic Charges to Model Molecular Polarization.

We review different models for introducing electrical polarization in force fields, with special focus on methods where polarization is modelled at the atomic charge level. While electric polarization has been...

(NH4)3FeF6 Mesocrystal Grown by Electric Field-Assisted in-situ Dissolution and Reaction of Anodic Iron Oxides

(NH4)3FeF6 mesocrystalline octahedrons are formed by in-situ dissolution and reaction of anodic iron oxides, followed by a non-classical crystal growth process involving electrical polarization and subsequent alignment of primary (NH4)3FeF6...

Surface electric fields increase human osteoclast resorption through improved wettability on carbonate-incorporated apatite

Osteoclast-mediated bioresorption can be of an efficient means of incorporating the dissolution of biomaterials in the bone remodeling process. Because of compositionally and structurally close resemblance of biomaterials with the natural mineral phases of the bone matrix, synthetic carbonate-substituted hydroxyapatite (CA) is considered as an ideal clinical biomaterial. The present study therefore investigated the effects of electrical polarization on the surface characteristics and interactions with human osteoclasts of hydroxyapatite (HA) and CA. Electrical polarization was found to improve the surface wettability of these materials by increasing the surface free energy, and this effect was maintained for one month. Analyses of human osteoclast cultures established that CA subjected to a polarization treatment accelerated osteoclast resorption but did not affect the early differentiation phase or the adherent morphology of the osteoclasts as evaluated by staining. These data suggest that the surface characteristics of the CA promoted osteoclast resorption. The results of this work are expected to contribute to the design of cell-mediated biomaterials that can be resorbed by osteoclasts after fulfilling their primary function as a scaffold for bone regeneration.

Mechanisms of electrical polarization of disordered systems based on Al-substituted LiFe-oxospinel

The temperature-frequency dependences of the dielectric permittivity and conductivity of Li2O-Fe2O3-Al2O3 ceramics in the temperature range of 298-648 K were obtained by impedance spectroscopy. Their analysis indicates the presence of a fractal-like structure in the studied samples, the effect of which is manifested at low temperatures. To study the phenomenon of electric polarization associated with this structure, we used the generalized law of Jonscher. A significant dependence of the dispersion of dielectric and conductive properties of these spinel ceramics on the temperature and aluminum content in them was revealed.

Universal superlattice potential for 2D materials from twisted interface inside h-BN substrate

Lateral superlattices in 2D materials provide a powerful platform for exploring intriguing quantum phenomena, which can be realized through the proximity coupling in forming moiré pattern with another layer. This approach, however, is invasive, material-specific, and requires small lattice mismatch and suitable band alignment, largely limited to graphene and transition metal dichalcogenides (TMDs). Hexagonal boron nitride (h-BN) of antiparallel (AA′) stacking has been an indispensable building block, as dielectric substrates and capping layers for realizing high-quality van der Waals devices. There is also emerging interest on parallelly aligned h-BN of Bernal (AB) stacking, where the broken inversion and mirror symmetries lead to out-of-plane electrical polarization. Here we show the that laterally patterned electrical polarization at a nearly parallel interface within the h-BN substrate can be exploited to create noninvasively a universal superlattice potential in general 2D materials. The feasibility is demonstrated by first principle calculations for monolayer MoSe2, black phosphorus, and antiferromagnetic MnPSe3 on such h-BN. The potential strength can reach 200 meV, customizable in this range through choice of distance of target material from the interface in h-BN. We also find sizable out-of-plane electric field at the h-BN surface, which can realize superlattice potential for interlayer excitons in TMD bilayers as well as dipolar molecules. The idea is further generalized to AB-stacked h-BN subject to torsion with adjacent layers all twisted with an angle, which allows the potential and field strength to be scaled up with film thickness, saturating to a quasi-periodic one with chiral structure.