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1.
Covering Rules and Nearest Neighbour Configurations of the Dodecagonal Quasiperiodic Structure 下载免费PDF全文
A dodecagonal quasiperiodic structure can be generated by duster covering and the quasilattice is described in terms of the quasi-unit cell. We study the structural properties of the two-dimensional dodecagonal quasilattice in the covering scheme. The pair covering rules and the nearest neighbour configurations are determined. It is shown that the dodecagonal structure is more complicated than those of decagonal and octagonal quasilattices. 相似文献
2.
Jianlin Lei Renhui Wang Chengzheng Hu Di-hua Ding 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):21-30
General formulae for thermal diffuse scattering from quasicrystals are applied to the case of dodecagonal quasicrystals from
corresponding elasticity theory. Contours of constant diffuse scattering intensity are illustrated. Unlike ordinary crystals,
shapes of isointensity contours are much more complicated and vary even among the collinear Bragg spots. Diffuse scattering
patterns in the plane perpendicular to a given zone axis are associated with corresponding specific elastic constants. Information
about elastic constants can be extracted from quantitative analysis of diffuse scattering patterns.
Received 7 December 1998 and Received in final form 12 March 1999 相似文献
3.
Self-Similar Transformation and Vertex Configurations of the Octagonal Ammann-Beenker Tiling 下载免费PDF全文
Based on the matching rules for squares and rhombuses,we study the self-similar transformation and the vertex configurations of the Ammann-Beenker tiling.The structural properties of the configurations and their relations during the self-similar transformation are obtained.Our results reveal the distribution correlations of the configurations,which provide an intuitive understanding of the octagonal quasi-periodic structure and also give implications for growing perfect quasi-periodic tiling according to the local rules. 相似文献
4.
Plastic Deformation of Fine-Grained Al-Cu-Fe-(B) Icosahedral Poly-Quasicrystals at Elevated Temperature 下载免费PDF全文
Fine-grained Al-Cu-Fe-(B) icosahedral poly-quasicrystals (1QCs) as the main materials and fine-grained Al- Pd-Mn IQCs as the supplements, both prepared by powder metallurgy, are uniaxially deformed at vaNous temperatures and strain rates. The systematic study shows the dependences of curves of the true stress versus true strain on several parameters, such as temperature, strain rate and grain size. For Al-Cu-Fe IQCs with grain sizes of about 10-30μm, QC-specific intra-granular softening drop appears in the deformation curves at lower temperatures and/or faster strain rates, but disappears in those curves at higher temperatures and/or slower strain rates, which suggests that the inter-granular effects such as grain-boundary sliding should be taken into account to interpret the continuous hardening, similarly to conventional poly-crystals. For Al-Cu-Fe-B IQCs with smaller grain sizes of about 1 μm and fine-grained AI-Pd-Mn IQCs with grain sizes of about 10μm, QC- specific intra-granular softening drop is absent for all the deformation curves at the possible lowest temperature and fastest strain rate. This implies that the sma/ler the grain size, the more the inter-granular contribution. At the same time, due to the rapid recovery caused by intense diffusion in small-sized grains, the intra-granular quasicrystal lattice reorders rapidly from disordering, which also inhibits the intra-granular softening drop to some extent. 相似文献
5.
We discuss the high-temperature electronic and thermal properties of an icosahedral quasicrystal within the framework of the fractional multicomponent Fermi-surface model. When intervalley electron-phonon scattering sets in above a characteristic temperature T∗ of the order of the Debye temperature ΘD the quasicrystal becomes more “metallic”. In this regime the electrical conductivity and the electronic contribution to the thermal conductivity vary as T and T2, respectively. We predict that at elevated temperatures the electronic specific heat will vary faster than γT and the low-frequency Drude-type component of the optical conductivity σ1(ω) will gain weight. 相似文献
6.
In this Letter, the dynamic plane elasticity problems of 2D quasicrystals is considered. By use of the Fourier transform and matrix transformations the system is reduced to uncoupled ordinary differential equations. Fourier images of Green's functions for dynamic plane elasticity problems of 2D dodecagonal, pentagonal and decagonal quasicrystals are obtained explicitly by the suggested method. 相似文献
7.
Jiahong Ma 《Solid State Communications》2004,132(6):355-359
We study the Ising model on a two-dimensional quasilattice developed from the decagonal covering structure. The periodic boundary conditions are applied to a patch of rhombus-like covering pattern. By means of the Monte Carlo simulation and the finite-size scaling analysis the critical temperature is estimated as 2.317±0.002. Two critical exponents are obtained being 1/v=0.992±0.003 and η=0.247±0.002, which are close to the values of the two-dimensional regular lattices as well as the Penrose tilings. 相似文献
8.
General complex variable function method for solving plane elasticity and the dislocation problems of quasicrystals with point group 10 mm has been proposed. All the fields variables are expressed by four arbitrary analytic functions. Analytical displacement expressions for the dislocation problem of the quasicrystal is obtained. The interaction between two parallel dislocations is also discussed in detail. 相似文献
9.
P. Gong C.-Z. Hu X. Zhou L. Miao X. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):477-481
Since quasicrystals have positional and orientational
long-range order, they are essentially anisotropic. However, the
researches show that some physical properties of quasicrystals are
isotropic. On the other hand, quasicrystals have additional phason
degrees of freedom which can influence on their physical behaviours.
To reveal the quasicrystal anisotropy, we investigate the
quasicrystal elasticity and other physical properties, such as
thermal expansion, piezoelectric and piezoresistance, for which one
must consider the contributions of the phason field. The results indicate that:
for the elastic properties, within linear phonon domain all
quasicrystals are isotropic, and within nonlinear phonon domain the
planar quasicrystals are still isotropic but the icosahedral
quasicrystals are anisotropic. Moreover, the nonlinear elastic
properties due to the coupling between phonons and phasons may
reveal the anisotropic structure of QCs. For the other physical
properties all quasicrystals behave like isotropic media except for
piezoresistance properties of icosahedral
quasicrystals due to the phason field. 相似文献
10.
N. Destainville 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):119-123
We perform Transition matrix Monte Carlo simulations to evaluate the
entropy of rhombus tilings with fixed polygonal boundaries and
2D-fold rotational symmetry. We estimate the large-size limit of
this entropy for D=4 to 10. We confirm analytic predictions of
[N. Destainville et al., J. Stat. Phys. 120, 799
(2005) and M. Widom et al., J. Stat. Phys. 120, 837
(2005)], in particular that the large size and large D limits
commute, and that entropy becomes insensible to size, phason strain
and boundary conditions at large D. We are able to infer finite
D and finite size scalings of entropy. We also show that
phason elastic constants can be estimated for any D by measuring the
relevant perpendicular space fluctuations. 相似文献
11.
K. Schröter G. Wilde R. Willnecker M. Weiss K. Samwer E. Donth 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):1-5
High-resolution synchrotron-radiation powder diffraction experiments were performed to observe structural changes induced
by hydrogen loading in rapidly-quenched Ti-Zr-Ni alloy ribbons with dominant icosahedral character. Lattice expansion effects
due to hydrogen storage in Ti-Zr-Ni quasicrystals as well as phonon and phason disorder coefficients are obtained from an
analysis of diffraction linewidths.
Received: 26 August 1997 / Revised: 8 January 1998 / Accepted: 10 February 1998 相似文献
12.
We study the Brownian motion of an ensemble of single colloidal particles in a random square and a quasicrystalline potential
when they start from non-equlibrium. For both potentials, Brownian dynamics simulations reveal a widespread subdiffusive regime
before the diffusive long-time limit is reached in thermal equilibrium. We develop a random trap model based on a distribution
for the depths of trapping sites that reproduces the results of the simulations in detail. Especially, it gives analytic formulas
for the long-time diffusion constant and the relaxation time into the diffusive regime. Aside from detailed differences, our
work demonstrates that quasicrystalline potentials can be used to mimic aspects of random potentials. 相似文献
13.
J. Bachteler H.-R. Trebin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(3):299-306
The elastic theory of quasicrystals considers, in addition to the “normal” displacement field, three “phason” degrees of freedom.
We present an approximative solution for the elastic Green's function of icosahedral quasicrystals, assuming that the coupling
between the phonons and phasons is small.
Received: 18 December 1997 / Accepted: 6 March 1998 相似文献
14.
Gerardo G. Naumis A. Bazán M. Torres R. Quintero-Torres 《Physica B: Condensed Matter》2008,403(18):3179-3184
One of the few examples in which the physical properties of an incommensurable system reflect an underlying higher dimensionality is presented. Specifically, we show that the reflectivity distribution of an incommensurable one-dimensional cavity is given by the density of states of a tight-binding Hamiltonian in a two-dimensional triangular lattice. Such effect is due to an independent phase decoupling of the scattered waves, produced by the incommensurable nature of the system, which mimics a random noise generator. This principle can be applied to design a cavity that avoids resonant reflections for almost any incident wave. An optical analogy, by using three mirrors with incommensurable distances between them, is also presented. Such array produces a countable infinite fractal set of reflections, a phenomena which is opposite to the effect of optical invisibility. 相似文献
15.
We have studied fluid-solid phase transformations of materials interacting via the Dzugutov potential (Phys. Rev. A 46, R2984 (1992)). We present evidence from molecular dynamics simulations that this interaction does not exhibit a liquid phase.
If a mixed potential (r) is formed by a linear superposition of and the Lennard-Jones potential , then the liquid phase disappears at a fraction of less than 60% .
Received 15 June 1998 and Received in final form 8 July 1999 相似文献
16.
Atomic jumps in icosahedral (AlCu)Li quasicrystals and related structures have been studied by molecular dynamics simulations.
In quasicrystalline structures jumps exists with jump vectors much shorter than an average nearest neighbor distance. This
is a consequence of the phasonic degree of freedom. The jumps therefore are called flips and the sites connected by the jump
vector are denoted alternative positions. We find that the atoms in the quasicrystal structures studied here do not flip to
alternative positions as proposed and observed in decagonal or dodecagonal quasicrystals but jump to sites which are at least
an ordinary interatomic distance apart. Furthermore we observe two diffusion regimes: below about 55% of the melting temperature
only small (AlCu) atoms carry out ring processes whereas at higher temperatures both kinds of atoms contribute to long-range
diffusion.
Received 21 July 1999 相似文献
17.
Yu Li R.W. Peng G.J. Jin Mu Wang X.Q. Huang A. Hu S.S. Jiang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):497-503
In the tight-binding approximation, we have investigated the behaviour of persistent currents in a one-dimensional Thue-Morse
mesoscopic ring threaded by a magnetic flux. By applying a transfer-matrix technique, the energy spectra and the persistent
currents in the system have been numerically calculated. It is shown that the flux-dependent eigenenergies form “band” structures
and the energy gaps will enlarge if the site energy increases. Actually, the site energy and the filling-up number of electrons
are two important factors which have much influence upon the persistent current. Increment of the site energy in the system
will lead to a dramatic suppression of the currents. When the highest-occupied energy level is on the top of the band, the
total current is limited; otherwise, the persistent current increases by several orders of magnitude. Generally, this kind
of large scale change in the magnitude of the current can easily be observed in the vicinity of band gaps. The parity effect
in the Thue-Morse ring is also discussed.
Received 22 January 2001 and Received in final form 25 October 2001 相似文献
18.
T. Janssen O. Radulescu A.N. Rubtsov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):85-95
Aperiodic crystals may have additional low frequency modes related to the possibility to describe them in a higher-dimensional
space. Dynamics associated with these degrees of freedom is called phasonic, but there are very different phenomena of this
type. A discussion is given of the use of the term. The relation between phason modes, the crystal structure, and the modulation
and sliding modes is discussed. Finally a relation with frictionless motion is studied.
Received 4 April 2002 / Received in final form 22 July 2002 Published online 17 September 2002 相似文献
19.
M. Hohl J. Roth H.-R. Trebin 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):595-601
The icosahedral or decagonal symmetry of quasicrystals is well described by a periodic structure in higher dimensions. One
consequence is the existence of dynamic phason modes in addition to the phonon modes. In an atomistic model phasons show up
as correlated atomic jumps. We detect the phasons by the calculation of correlation functions and the dynamical structure
factor in molecular dynamics simulations similar to the procedure used for phonons. In the simulations it is also possible
to observe atomic jump processes directly. The models studied here represent icosahedral AlCuLi and decagonal AlCuCo quasicrystals.
Ring processes are observed in the icosahedral case, and flips in the decagonal model.
Received 17 March 2000 and Received in final form 8 June 2000 相似文献
20.
It has recently been claimed that the dynamics
of long-wavelength phason fluctuations has been observed in
i-AlPdMn quasicrystals [S. Francoual et al.
Phys. Rev. Lett. 91, 225501 (2003);
A. Létoublon et al. 54, 753 (2001)]. We will show that
the data reported call for a more detailed development of
the elasticity theory of Jarić and Nelsson [M.V. Jarić and D.R. Nelsson, Phys. Rev. B 37,
4458 (1988)]
in order to determine the nature of small phonon-like atomic displacements
with a symmetry that follows the phason elastic constants.
We also show that a simple model with a single diffusing tile is sufficient
to produce a signal that (1) is situated at a “satellite position”
at a distance q from each Bragg peak; that (2) has an intensity that
scales with the intensity of the corresponding Bragg peak;
(3) falls off as 1/q2; and (4) has a time decay constant that is proportional to 1/Dq2.
It is thus superfluous to call for a picture of “phason waves” in order to explain such data, especially as such “waves” violate
many physical principles. 相似文献