Transition metal nitrides computations

Alloys Borates Solid-state Chemistry Carbides Transition Metal Solid-state Chemistry Chalcogenides Solid-state Chemistry Diffraction Methods in Inorganic Chemistry Electronic Structure of Solids Fluorides Solid-state Chemistry Halides Solid-state Chemistry Intercalation Chemistry Ionic Conductors Magnetic Oxides Magnetism of Extended Arrays in Inorganic Solids Nitrides Transition Metal Solid-state Chemistry Noncrystalline Solids Oxide Catalysts in Solid-state Chemistry Oxides Solid-state Chemistry Quasicrystals Semiconductor Interfaces Solids Characterization by Powder Diffraction Solids Computer Modeling Superconductivity Surfaces. 

A solid encapsulation, such as transition metal nanowires within boron nitride nanotubes, is a different system. Computationally, it is difficult to study, since the lattice constants of tube and wire have to be adjusted in an approach using periodic-boundary conditions. The energetics depend on the relation of the diameters of nanotube and eneapsulated nanowire. 

This is the first book devoted to the theoretical modelling of refractory carbides and nitrides and alloys based on them. It makes use of computational methods to calculate their spectroscopic, electric, magnetic, superconducting, thermodynamical and mechanical properties. Calculated results on the electronic band structure of ideal binary transition-metal carbides and nitrides are presented, and the influences of crystal lattice defects, vacancies and impurities are studied in detail. Data available on chemical bonding and the properties of multi-component carbide- and nitride-based alloys, as well as their surface electronic structure, are described, and compared with those of bulk crystals. 

The papers presented in the conference span the spectrum of activity in the science of alloys. The theoretical presentations ranged in content from fundamental studies of electronic structure, to first-principles calculations of phase diagrams, to the effects of charge transfer, to the temperature dependence of short-range order parameters. They encompassed the study of mechanical properties, the properties of dislocations, of phase evolution, and computer simulations. Experimental studies were presented based on a variety of state of the art experimental techniques, from TEM to synchrotron diffraction. The phenomena studied varied from the precipitation of nitrides in steel, to the wetting of interfaces between two different crystal structures, to the ordering of vacancies in carbides. And the materials whose properties were measured ranged from Transition metals, to the Lanthanides, to the Actinide series of compounds and alloys. 

Another example for an investigation of multinuclear transition metal clusters is the SOS-DFPT-IGLO study of the C shift tensors for interstitial carbides enclosed in carbonyl clusters. The interstitial shifts are important, both as a proof for the existence of an interstitial atom, and as a potential probe of electronic structure. Table 2 compares computed and experimental shifts. For the two rhodium clusters, it has been possible to compare not only isotropic shifts but the entire shift tensors, as an independent solid-state NMR study given the first tensor data for a number of interstitial carbides and nitrides. The overall agreement between computation and experiment is good, both for the isotropic shifts and for the available tensors. The largest deviation (43 ppm) was found... 

To illustrate the various types of covalent bonds occuring in transition metal carbides and nitrides, Herzig et al. (58) selected, in the band structures of TiC and TiN, representative k points that are characterized by a particular type of covalent interaction in more or less pure form. For the selected states, VEDs were computed using the results of full-potential LAPW band structure calculations. Each of Figs. 20-26 shows, in the top panel, a schematic representation of a special bond type and, in the bottom panel, the VED in a definite crystal plane for a... 

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