Structure Of Real Materials Research Articles

Functional Cubic Thin Films— A Structure View

Real structure of materials influences their physical properties. Thus, the understanding of the relationship between the structure parameters and the materials properties is a necessary basis for materials design. X-ray diffraction is a powerful experimental technique, which yields the required information about the microscopic and mesoscopic structure expressed in terms of lattice parameters, residual stress, microstrain, crystallite size, texture and crystal anisotropy. Application of advanced X-ray methods and related computational procedures is illustrated on a detailed structure study of cubic uranium nitride thin films that shows the connection between the microscopic and the mesoscopic structure parameters.

Local crystallography of crystals with disorder

Abstract The assumption of perfect periodicity in the crystal lattice is the most basic tenet of crystallography. However, many materials are not crystalline. Even when they are the atomic structure of real materials is often less than perfectly periodic, and usually deviations from perfect periodicity have significant effects on their properties. Thus in order to characterize the structure of real materials by diffraction the crystallographic approaches need to be complemented by other methods focusing on disorder. B. E. Warren was a pioneer of such alternative, non-crystallographic approaches, including the method of atomic pair-density function (PDF) analysis. With the advent of synchrotron based radiation sources, such as pulsed neutron sources and synchrotron radiation sources, it recently became possible to apply the PDF technique on crystals with and without disorder, covering the whole spectrum of structural order and disorder. Here some of the recent progresses in this approach made in my research group are reviewed.

ARPES spectral function near a Mott transition

Abstract An interpolation formula, connecting the high and low energy expansions of a momentum resolved Green function G ( k , ω ) was first outlined in: K. Matho, J. Phys. Chem. Solids 56 (1995) 1735. Here, the algorithm is presented in detail, allowing to calculate the interpolated spectrum for all energies. The high energy part is given by a Pade approximant of arbitrary order. The low energy scenario, with a large Fermi surface, is either backed up by microscopic manybody theory or suggested by phenomenological considerations. The algorithm itself decides, whether the two scenarios to be interpolated are compatible with each other. As an application, we give an in depth discussion of a correlated photohole, as observable in photoemission experiments. The emphasis is on experimental and theoretical exploration of generic low energy features, in agreement with the overall electronic structure of real materials. The context of doped, metallic Mott–Hubbard systems is chosen to indicate ways of modeling correlated spectra in the presence of strong onsite repulsion U and in finite dimension d =2 or d =3.

The structure of real materials using x-ray and neutron scattering

Recent advances have been made in the characterization of materials using x-ray and neutron scattering, particularly in studies of defects and short-range order. High flux, broad-band energy turnable x-ray and neutron sources coupled with high-speed computing are now allowing crystalline imperfections to be studied in unprecdented detail.

New applications of the Rehbinder effect in tribology. A review

The main solutions of typical elastic-plastic problems (including the tribocontact one) of physicochemical mechanics for surface-plasticized and surface-hardened materials are reviewed. The influence of surface-active media and residual stresses arising in the near-surface layers of solids after the ‘loading-unloading’ cycle of the real material structure, including distributions of linear and point lattice defects in soft and hard structural material components, is analysed. The role of the Rehbinder effect in establishing the antiwear mode of working conditions for real sliding tribopairs is shown by particular examples.