摘要:

Diffraction patterns from many different icosahedral quasicrystals exhibit localized diffuse scattering that typically takes the form of partial spherical shells in reciprocal space. Although many theoretical models for these shells have been proposed, none of these models adequately explains all the experimental observations. A new model based upon local α-phase coordination of bonded Mackay clusters in the icosahedral phase is presented. Diffraction simulations successfully predict most of the observed diffuse scattering features.

ISSN:0950-0839    

DOI:10.1080/09500839508241284

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The atomic structure of the σ= 5, (310)[001] grain boundary in NiAl has been determined by a synergistic approach using high-resolution electron microscopy and atomistic structure calculations. These calculations employ N-body empirical potentials which were developed for the NiAl phase. A minimum-energy structure was determined which produced calculated images which matched experimental images of the boundary. The change in interfacial energy due to various defects at the grain boundary was also examined. This is the, first concurrent application of experimental and theoretical structure determinations to a grain boundary in an intermetallic compound.

ISSN:0950-0839    

DOI:10.1080/09500839508241285

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The problem of spurious increase in volume fraction of second-phase particles during computer simulations of coarsening is examined. The origin of this problem is traced to the use of too long a time step (used for numerical integration of growth rates with respect to time) which leads to small particles with large negative growth rates shrinking to negative radii at the end of the time step. Such a shrinkage to negative sizes has the effect of pumping solute into the system. It is therefore suggested that the length of the time step be chosen in accordance with the size of the smallest particle present in the system. It is shown that spurious increase in particle volume has a significant effect on the particle size distributions in the scaling regime (making them broader and more skewed in the Lifshitz-Slyozov-Wagner model). Its effect on coarsening kinetics, however, is found to be small.

ISSN:0950-0839    

DOI:10.1080/09500839508241286

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Quasiperiodic binary tilings B1, B2 and B3 can be viewed as the superposition of two fivefold quasiperiodic tilings. Two fivefold quasiperiodic tilings F1 and F2 related to the binary tiling B3 are discussed. The subunits of the Al‒Mn‒Pd decagonal quasicrystal are consistent with the tiles in the fivefold quasiperiodic tilings. An ideal quasilattice of the Al‒Mn‒Pd decagonal quasicrystal can be regarded as an alternating stacking of the F1 and F2 quasilattices.

ISSN:0950-0839    

DOI:10.1080/09500839508241287

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The dependence of the carrier velocity on the width of energy (diagonal) disorder for a model of amorphous solids is analysed using a numerical simulation technique. In contrast with the behaviour in the low-driving-field region where the carrier velocity always decreases with increasing disorder, for high bias fields, the presence of small amounts of disorder induces non-monotonic behaviour, showing a maximum of the carrier velocity at non-zero disorder strength. A discussion of this phenomenon in terms of the distribution of jumps in the three spatial directions of the system is carried out. Some evidence suggesting that this behaviour might occur in real materials is presented.

ISSN:0950-0839    

DOI:10.1080/09500839508241288

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor