A cross-platform program, VESTA, has been developed to visualize both structural and volumetric data in multiple windows with tabs. VESTA represents crystal structures by ball-and-stick, space-filling, polyhedral, wireframe, stick, dot-surface and thermal-ellipsoid models. A variety of crystal-chemical information is extractable from fractional coordinates, occupancies and oxidation states of sites. Volumetric data such as electron and nuclear densities, Patterson functions, and wavefunctions are displayed as isosurfaces, bird's-eye views and two-dimensional maps. Isosurfaces can be colored according to other physical quantities. Translucent isosurfaces and/or slices can be overlapped with a structural model. Collaboration with external programs enables the user to locate bonds and bond angles in the `graphics area', simulate powder diffraction patterns, and calculate site potentials and Madelung energies. Electron densities determined experimentally are convertible into their Laplacians and electronic energy densities.

VESTA: a three-dimensional visualization system for electronic and structural analysis

Statistical physics has proven to be a fruitful framework to describe phenomena outside the realm of traditional physics. Recent years have witnessed an attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. A wide list of topics are reviewed ranging from opinion and cultural and language dynamics to crowd behavior, hierarchy formation, human dynamics, and social spreading. The connections between these problems and other, more traditional, topics of statistical physics are highlighted. Comparison of model results with empirical data from social systems are also emphasized.

Statistical physics of social dynamics

Since the subject of traffic dynamics has captured the interest of physicists, many surprising effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by ``phantom traffic jams'' even though drivers all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction in the volume of traffic cause a lasting traffic jam? Under which conditions can speed limits speed up traffic? Why do pedestrians moving in opposite directions normally organize into lanes, while similar systems ``freeze by heating''? All of these questions have been answered by applying and extending methods from statistical physics and nonlinear dynamics to self-driven many-particle systems. This article considers the empirical data and then reviews the main approaches to modeling pedestrian and vehicle traffic. These include microscopic (particle-based), mesoscopic (gas-kinetic), and macroscopic (fluid-dynamic) models. Attention is also paid to the formulation of a micro-macro link, to aspects of universality, and to other unifying concepts, such as a general modeling framework for self-driven many-particle systems, including spin systems. While the primary focus is upon vehicle and pedestrian traffic, applications to biological or socio-economic systems such as bacterial colonies, flocks of birds, panics, and stock market dynamics are touched upon as well.

Traffic and related self-driven many-particle systems

A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Perspective on the Development of Lead-free Piezoceramics

Statistical physics of vehicular traffic and some related systems

The antiferroelectric Goldstone mode in a free-standing film was investigated by means of the electro-optic measurement. The divergence of the relaxation time corresponding to the divergence of the helical pitch was observed. In comparison with the result obtained in a homogeneous cell the surface anchoring effect is discussed.

Electro-Optic Effect in an Antiferroelectric Liquid Crystal

On the 74 K Phase Transition in Hexagonal Barium Titanate

Optical characterization of tungstic acid during gelation process was performed by observing the evolution of the angular dependence of the scattered light intensity and the penetration length of the light beam. In the light scattering experiments, the anisotropic increase or decrease in the scattered-light intensity was observed after the gelation time ( t g ). In the observation of the penetration length of the light beam, the drastic change in the decreasing rate of the penetration length was found also around t g . The light intensity scattered from the positions adjacent to the incident light beam increased remarkably after t g . Judging from these characteristic features around t g , the light scattering properties seem to be closely correlated with the formation of the network in the later stage of the gelation process.

Optical Characterization of Tungstic Acid around Gelation Time

Melt-growth of CsCl under high pressure

Nonlinear responses are discussed on the basis of the kinetic equation, where the use is made of the thermodynamic potential functions. Using the obtained expressions as the function of frequency, the after-effect functions are derived through their Fourier-transform

Yoshihiro Ishibashi

Papers

Electro-Optic Effect in an Antiferroelectric Liquid Crystal

On the 74 K Phase Transition in Hexagonal Barium Titanate

Optical Characterization of Tungstic Acid around Gelation Time

Melt-growth of CsCl under high pressure

A phenomenological theory of nonlinear responses