scholarly journals Elastic Softening in Nanocrystalline Silicon

1989 ◽  
Vol 153 ◽  
Author(s):  
S. R. Phillpot ◽  
D. Wolf ◽  
J. F. Lutsko
Keyword(s):  
Grain Boundary ◽  
Elastic Moduli ◽  
Nanocrystalline Material ◽  
Structural Disorder ◽  
Nanocrystalline Silicon ◽  
Three Body ◽  
Body Potential ◽  
Twist Boundaries ◽  
Modulation Wavelength ◽  
Elastic Softening

AbstractIt is pointed out that some of the generic physical properties of a nanocrystalline material are similar to those of a grain-boundary superlattice. The structure and elastic properties of a superlattice of twist boundaries on the (110) plane of silicon are calculated as a function of modulation wavelength using a three-body potential. All elastic moduli are found to be softened. This softening is attributed to the relatively small amount of structural disorder at the interfaces.

On the elastic behavior of composition-modulated superlattices

1991 ◽  
Vol 6 (6) ◽  
pp. 1207-1218 ◽  
Author(s):  
J.A. Jaszczak ◽  
D. Wolf
Keyword(s):  
Grain Boundary ◽  
Structural Disorder ◽  
Lattice Parameter ◽  
Elastic Behavior ◽  
Parameter Mismatch ◽  
Fcc Metals ◽  
Anisotropic Lattice ◽  
Elastic Anomalies ◽  
Modulation Wavelength

Atomistic computer simulations are used to systematically investigate the role of interfacial disorder on the elastic behavior of composition-modulated superlattices of fcc metals, represented by simple Lennard–Jones potentials. The structures, energies, and average elastic properties of four types of superlattices with various degrees of interfacial disorder are computed as a function of the modulation wavelength along [001]. The four superlattice types studied include perfectly coherent, incoherent, and two types derived from these by introducing relative twists about [001] between alternating layers. A 20% lattice-parameter mismatch between the two modulating materials is assumed. Results are compared with our earlier work on unsupported thin films, grain-boundary superlattices, and incoherent superlattices with a 10% lattice-parameter mismatch. The degree of structural disorder at the interfaces is found to correlate well with the magnitude of the elastic anomalies, which cannot be accounted for by anisotropic lattice-parameter changes alone. The grain-boundary superlattices studied earlier are found to provide a good model limit for the elastic behavior of interfacially disordered dissimilar-material superlattices.

Microstructures of a-axis oriented YBCO films made by hybrid plasma sputtering

1995 ◽  
Vol 10 (4) ◽  
pp. 803-809 ◽  
Author(s):  
W. Ito ◽  
A. Oishi ◽  
S. Mahajan ◽  
Y. Yoshida ◽  
T. Morishita
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Anisotropic Growth ◽  
Plan View ◽  
Plasma Sputtering ◽  
Transmission Electron ◽  
Hybrid Plasma ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
Twist Boundaries

Microstructures of a-axis oriented YBa2Cu3O7−x films made by newly developed de 100 MHz hybrid plasma sputtering were investigated using transmission electron microscopy (TEM). The films deposited on (110) NdGaO3 and (100) SrTiO3 substrates were found to grow in a perfect epitaxial fashion and with clear interface. The plan view of the TEM image showed that both films were comprised of two kinds of grains having the c axis aligning along two perpendicular directions in the plane with equal probability. The structures of the grain boundary, however, were found to be very different for the two films from the plan views. The film on NdGaO3 showed a lot of twist boundaries, while the film on SrTiO3 consisted of many symmetrical tilt boundaries and basal-plane-faced tilt boundaries. The type of grain boundary is determined by the anisotropic growth rates of the film between c direction and a-b direction.

Ab Initio Calculation of a Three-Body Potential To Be Applied in Simulations of Fluid Neon

1998 ◽  
Vol 4 (3) ◽  
pp. 377-382 ◽  
Author(s):  
Elena Ermakova ◽  
Jan Solca ◽  
Gerold Steinebrunner ◽  
Hanspeter Huber
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Three Body ◽  
Body Potential

On Frequencies of Occurrence of Geometrically Characteristic Grain Boundaries

2013 ◽  
Vol 203-204 ◽  
pp. 427-430 ◽  
Author(s):  
Krzysztof Glowinski
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Data ◽  
Imaging Techniques ◽  
Serial Sectioning ◽  
Boundary Parameter ◽  
Statistical Studies ◽  
Point Groups ◽  
Twist Boundaries ◽  
Point Of Reference

Development of spatial microstructure imaging techniques (e.g. of automated serial sectioning) has made it possible to collect five macroscopic grain boundary parameters for sets of boundaries large enough for carrying out statistical studies. As a point of reference for future analysis of experimentally measured boundary data, various aspects of estimating the frequencies of occurrence of geometrically characteristic boundaries among random grain boundaries for the cases of cubic Oh, hexagonal D6h and tetragonal D4h point groups are discussed. Example frequencies, in particular for symmetric and improperly quasi-symmetric boundaries, are presented. Two approaches for verification whether a given boundary has a tilt or twist character are confronted, i.e. a method based on a distance function defined in the boundary parameter space and the widely known decomposition of a boundary into its tilt and twist components. The frequencies for tilt and twist boundaries calculated using both methods are compared.

Effect of Grain Boundary Energy Anisotropy on Faceting and Migration of Low Angle Grain Boundaries

2014 ◽  
Vol 783-786 ◽  
pp. 1634-1639
Author(s):  
Dmitri A. Molodov ◽  
Jann Erik Brandenburg ◽  
Luis Antonio Barrales-Mora ◽  
Günter Gottstein
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Boundary Energy ◽  
Migration Behavior ◽  
Grain Boundary Energy ◽  
Contrast Imaging ◽  
Orientation Contrast ◽  
And Migration ◽  
Twist Boundaries

The faceting and migration behavior of low angle <100> grain boundaries in high purity aluminum bicrystals was investigated. In-situ technique based on orientation contrast imaging was applied. In contrast to the pure tilt boundaries, which remained straight/flat and immobile during annealing at elevated temperatures, mixed tilt-twist boundaries readily assumed a curved shape and steadily moved under the capillary force. Computational analysis revealed that this behavior is due to the inclinational anisotropy of grain boundary energy, which in turn depends on boundary geometry – the energy of pure tilt low angle <100> boundaries is anisotropic, whereas that of mixed tilt-twist boundaries isotropic with respect to boundary inclination.

Static Three-Body Potential in Baryons

1998 ◽  
Vol 15 (8) ◽  
pp. 555-557
Author(s):  
Jue-ping Liu ◽  
Ping Wang
Keyword(s):  
Three Body ◽  
Body Potential

Numerical Study of Grain Boundary Diffusion in Nanocrystalline Materials

2005 ◽  
Vol 237-240 ◽  
pp. 1043-1048 ◽  
Author(s):  
D. Gryaznov ◽  
J. Fleig ◽  
Joachim Maier
Keyword(s):  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Boundary Diffusion ◽  
Nanocrystalline Material ◽  
Numerical Study ◽  
Average Length ◽  
Type A ◽  
Grain Boundary Diffusion ◽  
Conventional Models ◽  
Diffusion Profiles

Diffusion in nanocrystalline materials is becoming an increasingly important topic. The analysis of diffusion profiles obtained in nanocrystalline materials with enhanced grain boundary diffusion, however, is not straightforward since assumptions made in the deviation of the conventional models are often not fulfilled. In this contribution numerical diffusion studies are performed in order to investigate effects caused by the high density of interfaces in nanocrystalline material. A continuum model based on the 2D 2-nd Fick’s law was solved by means of the finite element method. This allows us to analyze diffusion profiles for different geometrical situations such as a single boundary, square grains with the grain size of 80 nm and 25 nm and geometries comprising differently oriented boundaries of the average length of 30 nm . The analysis was carried out for different diffusion lengths corresponding to Harrison type A and type B kinetic regimes. For the isolated boundary a very good agreement was achieved in comparison with the classical Whipple’s solution. For nanocrystalline material, however, considerable errors can occur when analyzing the averaged diffusion profiles in the conventional Harrison type A and B kinetics.

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