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

Dielectric properties of the disordered and ordered Pb(In 1/2 Nb 1/2 )O 3 (abbreviated as PIN) single crystals were investigated in the range of temperature T from -70 to 200°C and of hydrostatic pressures p up to 0.7 GPa. For the disordered PIN, a typical dielectric dispersion which obeys the empirical Vogel-Fulcher relation was observed. Such dielectric dispersion strength was weakened with an increase in the degree of chemical ordering (S) at the B-site cations in the perovskite ABO 3 , and then relaxor behavior disappears. The relaxor behavior was also weakened with increasing pressure up to 0.7 GPa for the quenched disordered PIN with S=0.2, whereas for the disordered PIN with S=0.4, the relaxor behavior was weakened with increasing pressure and then the antiferroelectric phase transition was induced by the application of pressure above 0.4 GPa. For the ordered PIN, the phase below the transition temperature was confirmed to be antiferroelectric by observation of P - E double hysteresis loops. The st...

The Temperature and Pressure Dependence of the Dielectric Properties of Disordered and Ordered Pb(In1/2Nb1/2)O3 Single Crystals.

The fundamental aspects of the structure, the energies of the formation and of the activation of domain walls are reviewed for several one-dimensional model systems. The effect of discreteness of atomic lattices on the structure and the activation energy of domain walls is described. The motion of walls will be also mentioned.

Structure and physical properties of domain walls

The Kolmogorov-Avrami-type formulation for both the latent nucleation (inhomogeneous) and the random nucleation (homogeneous) cases is presented for finite systems. In finite systems, there appear three time regimes. For the latent nucleus case the fraction of transformed regions remains as 1- e - N V ( N : density of nuclei, V : system volume) and for the random nucleation case it approaches unity in the time dependence as 1- A e - J V t ( A : constant, J : nucleation rate). The growth rate in finite systems is always smaller than that in infinite systems. We present the numerical results of one-dimensional system as an example.

A Statistical Theory of Nucleation and Growth in Finite Systems

The phenomenological theory of the 90° ferroelectric domain wall previously proposed is reviewed. It has turned out that it is the depolarizing field effect that distinguishes the stable head-to-tail wall from the unstable head-to-head wall energetically. The previous model is modified to take the effect of the depolarization field into account. The increment in the domain wall energy due to the depolarizing field is discussed.

A Theory of Ferroelectric 90 Degree Domain Wall

A simple computational method is presented for the activation energy of thick domain walls. It is based upon the Cauchy integral representation of the energy density function, Some examples are shown.

Yoshihiro Ishibashi

Papers

The Temperature and Pressure Dependence of the Dielectric Properties of Disordered and Ordered Pb(In1/2Nb1/2)O3 Single Crystals.

Structure and physical properties of domain walls

A Statistical Theory of Nucleation and Growth in Finite Systems

A Theory of Ferroelectric 90 Degree Domain Wall

Computational Method of Activation Energy of Thick Domain Walls