Ferroelectricity Induced by a Combination of Crystallographic Chirality and Axial Vector.

Ferroelectric materials compatible with magnetism and/or conductive properties provide a platform for exploring unconventional phenomena, such as the magnetoelectric effect, nonreciprocal responses, and nontrivial superconductivity. Though recent studies on multiferroics have offered several approaches, the search for magnetic and/or conducting ferroelectric materials is still a challenging issue under the traditional "d-ness" rule, refusing active d electrons. Here, we propose the emergence of ferroelectricity through a combination of crystallographic chirality and axial vector, accepting even non-d magnetic ions.

Crystal structure and properties of perovskite-type rubidium niobate, a high-pressure phase of RbNbO.

We synthesized a perovskite-type RbNbO at 1173 K and 4 GPa from non-perovskite RbNbO and investigated its crystal structure and properties towards ferroelectric material design. Single-crystal X-ray diffraction analysis revealed an orthorhombic cell in the perovskite-type structure (space group 2, no. 38) with = 3.

Atomic-Level Changes during Electrochemical Cycling of Oriented LiMnO Cathodic Thin Films.

Spinel LiMnO is an attractive lithium-ion battery cathode material that undergoes a complex series of structural changes during electrochemical cycling that lead to rapid capacity fading, compromising its long-term performance. To gain insights into this behavior, in this report we analyze changes in epitaxial LiMnO thin films during the first few charge-discharge cycles with atomic resolution and correlate them with changes in the electrochemical properties. Impedance spectroscopy and scanning transmission electron microscopy are used to show that defect-rich LiMnO surfaces contribute greatly to the increased resistivity of the battery after only a single charge.

Chemical design of a new displacive-type ferroelectric.

Since the discovery of the ferroelectric perovskite-type oxide BaTiO in 1943, numerous materials have been surveyed as candidates for new ferroelectrics. Perovskite-type materials have played a leading role in basic research and applications of ferroelectric materials since the last century. Experimentalists and theoreticians have developed a new materials design stream for post-perovskite materials.

Oxide-ion diffusion in brownmillerite-type CaAlMnO from first-principles calculations.

Oxide-ion diffusion pathways in brownmillerite oxides CaAlMnO and CaAlMnO are systematically investigated using first-principles calculations. These structures reversibly transform into each other by oxidation and reduction. We examine oxide-ion migration in CaAlMnO and CaAlMnO using the nudged elastic band method.

Revealing Spatial Distribution of Al-Coordinated Species in a Phase-Separated Aluminosilicate Glass by STEM-EELS.

Structure determination of glass remains an important issue in glass science. The electron microscope with its high spatial resolution and versatile functions has been widely applied to observe phase separation and structural heterogeneity in glass. While elemental analysis such as energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) may provide local compositional information with nanometer-scale resolution, structural information in a glass network cannot be directly obtained.

Quantitative prediction of grain boundary thermal conductivities from local atomic environments.

Quantifying the dependence of thermal conductivity on grain boundary (GB) structure is critical for controlling nanoscale thermal transport in many technologically important materials. A major obstacle to determining such a relationship is the lack of a robust and physically intuitive structure descriptor capable of distinguishing between disparate GB structures. We demonstrate that a microscopic structure metric, the local distortion factor, correlates well with atomically decomposed thermal conductivities obtained from perturbed molecular dynamics for a wide variety of MgO GBs.

Density functional study of the phase stability and Raman spectra of YbO, YbSiO and YbSiO under pressure.

The phase stability and Raman spectra of Yb2O3, Yb2SiO5 and Yb2Si2O7 under hydrostatic pressure are investigated using density functional theory calculations. The calculated energies of polymorphs of each compound show that the stable phases at zero pressure, viz., C-type Yb2O3, X2-Yb2SiO5 and β-Yb2Si2O7, exhibit a pressure-induced phase transition as compressive pressure increases, which is consistent with available experimental data.

Impact of local strain on Ti-L₂,₃ electron energy-loss near-edge structures of BaTiO₃: a first-principles multiplet study.

Identification of local strains is crucial because the local strains largely influence the ferroelectric property of BaTiO₃. The effects of local strains induced by external pressures on the Ti-L₂,₃ electron energy-loss near-edge structure (ELNES) of BaTiO₃ were theoretically investigated using first-principles multiplet calculations. We revealed that the effects appear in the position of the spectral threshold, namely the spectrum shifts to lower and higher energy sides by the tensile and compressive pressures, respectively.

First-principles calculations of lithium-ion migration at a coherent grain boundary in a cathode material, LiCoO(2).

Results of theoretical calculations are reported, examining the effect of a coherent twin boundary on the electrical properties of LiCoO(2) . This study suggests that internal interfaces in LiCoO(2) strongly affect the battery voltage, battery capacity, and power density of this material, which is of particular concern if it is used in all-solid-state Li-ion batteries.