The Energetics of Li Off-Centering in K1−x_{1-x}Lix_xTaO3_3; First Principles Calculations

K$_{1-x}$Li$_{x}$TaO$_3$ (KLT) solid solutions exhibit a variety of interesting physical phenomena related to large displacements of Li-ions from ideal perovskite A-site positions. First-principles calculations for KLT supercells were used to investigate these phenomena. Lattice dynamics calculations for KLT exhibit a Li off-centering instability. The energetics of Li-displacements for isolated Li-ions and for Li-Li pairs up to 4th neighbors were calculated. Interactions between nearest neighbor Li-ions, in a Li-Li pair, strongly favor ferroelectric alignment along the pair axis. Such Li-Li pairs can be considered "seeds" for polar nanoclusters in KLT. Electrostriction, local oxygen relaxation, coupling to the KT soft-mode, and interactions with neighboring Li-ions all enhance the polarization from Li off-centering. Calculated hopping barriers for isolated Li-ions and for nearest neighbor Li-Li pairs are in good agreement with Arrhenius fits to experimental dielectric data.Comment: 14 pages including 10 figures. To Physical Review B. Replaced after corrections due to referees' remark

Estimation of a condition of electromagnetic relays a method of acoustic diagnostics in systems of railway automatics

The paper deals with methods of preliminary analysis of sound signals to extract stable features in classifying the relay used in railway automation systems. The algorithm of the description of a sound signal on the basis of these attributes is offered

PbTiO3 nanoparticles embedded in a liquid crystalline elastomer matrix: Structural and ordering properties

Ferroelectric PbTiO3 nanoparticles were synthesized to be used as inorganic components of new composite materials based on a liquid crystalline elastomer (LCE) matrix. The preparation and characterization of the composite materials, with a relatively high concentration of PbTiO3 nanoparticles, in the form of thin films is described. The composite films retain the thermomechanical response typical of standard LCEs and the nanoparticles are distributed in the film in anisotropic structures indicating the presence of a coupling between the LCE ordered matrix and the nanomaterials. The nematoelastic coupling and the supercritical nature of the paranematic-nematic transition of the LSCE-based composites was verified also in the presence of ferroelectric nanoparticles