Table of contents

We would like to make corrections to three equations in the above article. Please see the PDF file for full details.

Most manganites exhibiting colossal magnetoresistant properties are structurally very simple. They are based on a perosvskite structure with the general formula . The electric and magnetic properties strongly depend on the composition (A, A', x) and eventually on the exact oxygen content. These changing properties are strongly related to structural and microstructural changes. Indeed, the structure has many degrees of freedom. The MnO₆ octahedra can not only deform, they can also rotate along their fourfold or twofold axis, giving rise to different superstructures or modulated structures. This will lower the symmetry of the structure from cubic to orthorhombic, rhombohedral or monoclinic. A lowering in symmetry will of course introduce different orientation variants (twins) and translation variants (antiphase boundaries). These microstructural changes are reviewed here through a transmission electron microscopy study of bulk as well as thin film colossal magnetoresistance materials.

For thin films grown on a single crystal substrate the misfit with the substrate is another very important parameter, which determines the structure and the microstructure. We review different methods of accommodating the stress induced by the substrate: elastically, through interface dislocations, through pseudo-periodic twinning, through formation of antiphase domains or through a phase transition in the film.

A large number of polycrystalline materials, both manmade and natural, display preferred orientation of crystallites. Such alignment has a profound effect on anisotropy of physical properties. Preferred orientation or texture forms during growth or deformation and is modified during recrystallization or phase transformations and theories exist to predict its origin. Different methods are applied to characterize orientation patterns and determine the orientation distribution, most of them relying on diffraction. Conventionally x-ray pole-figure goniometers are used. More recently single orientation measurements are performed with electron microscopes, both SEM and TEM. For special applications, particularly texture analysis at non-ambient conditions, neutron diffraction and synchrotron x-rays have distinct advantages. The review emphasizes such new possibilities.

A second section surveys important texture types in a variety of materials with emphasis on technologically important systems and in rocks that contribute to anisotropy in the earth. In the former group are metals, structural ceramics and thin films. Seismic anisotropy is present in the crust (mainly due to phyllosilicate alignment), the upper mantle (olivine), the lower mantle (perovskite and magnesiowuestite) and the inner core (ε-iron) and due to alignment by plastic deformation. There is new interest in the texturing of biological materials such as bones and shells. Preferred orientation is not restricted to inorganic substances but is also present in polymers that are not discussed in this review.

Earthquakes occur as a result of global plate motion. However, this simple picture is far from complete. Some plate boundaries glide past each other smoothly, while others are punctuated by catastrophic failures. Some earthquakes stop after only a few hundred metres while others continue rupturing for a thousand kilometres. Earthquakes are sometimes triggered by other large earthquakes thousands of kilometres away. We address these questions by dissecting the observable phenomena and separating out the quantifiable features for comparison across events. We begin with a discussion of stress in the crust followed by an overview of earthquake phenomenology, focusing on the parameters that are readily measured by current seismic techniques. We briefly discuss how these parameters are related to the amplitude and frequencies of the elastic waves measured by seismometers as well as direct geodetic measurements of the Earth's deformation. We then review the major processes thought to be active during the rupture and discuss their relation to the observable parameters. We then take a longer range view by discussing how earthquakes interact as a complex system. Finally, we combine subjects to approach the key issue of earthquake initiation. This concluding discussion will require using the processes introduced in the study of rupture as well as some novel mechanisms. As our observational database improves, our computational ability accelerates and our laboratories become more refined, the next few decades promise to bring more insights on earthquakes and perhaps some answers.

As the size of modern electronic and optoelectronic devices is scaling down at a steady pace, atomistic simulations become necessary for an accurate modelling of their structural, electronic, optical and transport properties. Such microscopic approaches are important in order to account correctly for quantum-mechanical phenomena affecting both electronic and transport properties of nanodevices. Effective bulk parameters cannot be used for the description of the electronic states since interfacial properties play a crucial role and semiclassical methods for transport calculations are not suitable at the typical scales where the device behaviour is characterized by coherent tunnelling.

Quantum-mechanical computations with atomic resolution can be achieved using localized basis sets for the description of the system Hamiltonian. Such methods have been extensively used to predict optical and electronic properties of molecules and mesoscopic systems.

The most important approaches formulated in terms of localized basis sets, from empirical tight-binding (TB) to first principles methods, are here reviewed. Being a full band approach, even the simplest TB overcomes the limitations of envelope function approximations, such as the well-known k · p, and allows to retain atomic details and realistic band structures. First principles calculations, on the other hand, can give a very accurate description of the electronic and structural properties.

Transport in nanoscale devices cannot neglect quantum effects such as coherent tunnelling. In this context, localized basis sets are well-suited for the formal treatment of quantum transport since they provide a simple mathematical framework to treat open-boundary conditions, typically encountered when the system eigenstates carry a steady-state current.

We review the principal methods used to formulate quantum transport based on local orbital sets via transfer matrix and Green's function (GF) techniques. We start from a general introduction to the scattering theory which leads to the Landauer formula, and then report on the most recent progresses of the field including the application of the self-consistent non-equilibrium GF formalism.