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

Evolution of the light scattering and electrical properties of the tungstic acid during the gelation process has been investigated. The scattered light becomes anisotropic and the depolarized scattering grows strong around 2 hours after the beginning of gelation. On the other hand, the resistance shows a steady increase. With the results obtained from the present study, we concluded that the light scattering mechanism changes from the Rayleigh scattering to the Mie scattering with the progress of gelation.

Evolution of Light Scattering and Electrical Properties of Tungsten Oxide Gel

A two-sublattice model is presented for interpreting the appearance of the phase sequence Normal-Commensurate-Incommensurate-Commensurate phases such as seen in (C3H7NH3)2MnCl4.

A Phenomenological Theory of the Transition Sequence including an Incommensurate (Commensurate) Phase Sandwiched by Reentrant Commensurate (Incommensurate) Phase

The polarization reversal process in the surface-stabilized ferroelectric liquid crystal was studied with a polarizing microscope utilizing a stroboscopic method. Domain patterns appearing during the polarization reversal were analyzed in terms of the spatial correlation function based upon the Avrami model of the crystal growth.

Pattern Evolution in a Polarization Reversal of Ferroelectric Liquid Crystal

The growth process of the cholesteric finger pattern, appearing in a large pitch cholesteric liquid crystal sandwiched between glass plates, has been experimentally investigated. Depending on the cell gap and the external electric field, several patterns of different kinds are observed. The characteristic feature of the patterns is extracted from the observed image and then the dynamical behavior of the patterns is discussed. Moreover, the formation process of the dendritic finger pattern is analyzed on the basis of the Avrami model.

Experimental Study of the Growth of the Cholesteric Finger Pattern.

The assumption of gaussian distribution of relaxation times adopted by Hill and Ichiki for the explanation of experimental data on frequency dependence of dielectric constants e of TGS and DKDP is examined. It is known that the above assumption is inadequate since it fails to predict the critical slowing down around the phase transition temperature. It is shown analytically that the above assumption is not suitable for the explanation of e in high frequency region. An alternative distribution function of relaxation times is shown.

Yoshihiro Ishibashi

Papers

Evolution of Light Scattering and Electrical Properties of Tungsten Oxide Gel

A Phenomenological Theory of the Transition Sequence including an Incommensurate (Commensurate) Phase Sandwiched by Reentrant Commensurate (Incommensurate) Phase

Pattern Evolution in a Polarization Reversal of Ferroelectric Liquid Crystal

Experimental Study of the Growth of the Cholesteric Finger Pattern.

On Distribution of Relaxation Times in Some Ferroelectrics