Results 1 - 10 of 8086
Results 1 - 10 of 8086. Search took: 0.029 seconds
|Sort by: date | relevance|
[en] A finite element formulation which derives constitutive response from crystal plasticity theory is used to examine localized deformation in fcc polycrystals. The polycrystals are simple, idealized arrangements of grains. Localized deformations within individual grains lead to the development of domains that are separated by boundaries of high misorientation. Shear banding is seen to occur on a microscopic scale of grain dimensions. The important consequences of these simulations are that the predicted local inhomogeneities are meeting various requirements which make them possible nucleation sites for recrystallization
[en] The migration mechanism of the interstitial dumbbell in a FCC (face centered cubic) lattice constrains its path on a sublattice with a coordination number of 8. In a random binary alloy AB, in which only species B has a noticeable mobility, the long range migration of the dumbbell defect is possible only if the concentration of B is larger than the percolation threshold ρc on the sublattice. Standard techniques have been employed to get a first evaluation of this threshold: the cluster density n(s) is obtained after an automatic counting of the clusters up to a size of 15 and a d-Log Pade approximants analysis of the various moments of this density function is performed. The use of a recent conjecture concerning the critical behaviour of the moments of n(s) in the neighbourhood of ρc helps us to extract simultaneously from our data reasonable values of the critical exponents β and α, together with a value of ρc = 0.2780 + 0.0005. (Author). 16 refs., 15 figs., 7 tabs
[en] The magnetic susceptibility of f.c.c. protactinium monocarbide was measured by the Faraday method between 4K and room temperature. In this temperature range, the magnetic susceptibility of PaC is very weak (about - 50.10-6 u.e.m. c.g.s/mole) and essentially temperature independent, indicating the absence of 5f electrons and the pentavalent character of Pa in this compound
[en] A recently proposed analytic nearest-neighbour model for fcc metals is criticised and two alternative nearest-neighbour models derived from the separable potential method (SPM) are recommended. Results for copper and aluminium illustrate the utility of the recommended models. (author). 20 refs, 5 tabs
[en] Close-packed clusters of vacancies are those in which every vacancy has at least one other vacancy in a nearest neighbour position. Recently a study has been carried out of the possible configurations of small clusters of this type in all single lattice structures [see Phil. Mag., vol. 32, p. 379 (1975)]. This work is now being extended to consider the migration, growth and contraction of clusters and results for the face centred cubic structure are presented. (Auth.)
[en] In many problems in molecular and solid state structures one seeks to determine the energy-minimizing decoration of sites with different atom types. In other problems, one is interested in finding a decoration with a target physical property (e.g. alloy band gap) within a certain range. In both cases, the sheer size of the configurational space can be horrendous. We present two approaches which identify either the minimum-energy configuration or configurations with a target property for a fixed underlying Bravais lattice. We compare their efficiency at locating the deepest minimum energy configuration of face centered cubic Au-Pd alloy. We show that a global-search genetic-algorithm approach with diversity-enhancing constraints and reciprocal-space mating can efficiently find the global optimum, whereas the local-search virtual-atom approach presented here is more efficient at finding structures with a target property
[en] Here, we propose a strategy for robust high-quality self-assembly of nontrivial periodic structures out of patchy particles and investigate it with Brownian dynamics simulations. Its first element is the use of specific patch-patch and shell-shell interactions between the particles, which can be implemented through differential functionalization of patched and shell regions with specific DNA strands. The other key element of our approach is the use of a layer-by-layer protocol that allows one to avoid the formation of undesired random aggregates. As an example, we design and self-assemble in silico a version of a double diamond lattice in which four particle types are arranged into bcc crystal made of four fcc sublattices. The lattice can be further converted to cubic diamond by selective removal of the particles of certain types. These results demonstrate that by combining the directionality, selectivity of interactions, and the layer-by-layer protocol, a high-quality robust self-assembly can be achieved.
[en] The effect of Cu addition on the (α1 + α2) miscibility gap of the Al-Zn binary system was studied at 360 oC by using the diffusion couple technique. It was experimentally verified that the highest temperature of the (α1 + α2) miscibility gap of the Al-Zn system is significantly increased by the addition of Cu. The miscibility gap of Al-Zn-Cu face-centered cubic solid solution becomes smaller with the addition of Zn than that of the Al-Cu binary system above 351 oC, which is in agreement with previous thermodynamic predictions.
[en] The characteristics of quasi-breathers in monatomic fcc metals are investigated by the molecular dynamics method. The standard deviations of the frequencies of atoms constituting a breather from the fundamental frequency of oscillations are calculated. It is shown that the quasi-breather lifetime in the models under investigation depends on the initial excitation conditions as well as on the metal type.