Dubois J.-M.,CNRS Jean Lamour Institute
Chemical Society Reviews | Year: 2012
This article aims at an account of what is known about the potential for applications of quasicrystals and related compounds, the so-called family of Complex Metallic Alloys (CMAs‡). Attention is focused at aluminium-based CMAs, which comprise a large number of crystalline compounds and quasicrystals made of aluminium alloyed with transition metals (like Fe or Cu) or normal metals like Mg. Depending on composition, the structural complexity varies from a few atoms per unit cell up to thousands of atoms. Quasicrystals appear then as CMAs of ultimate complexity and exhibit a lattice that shows no periodicity anymore in the usual 3-dimensional space. Properties change dramatically with lattice complexity and turn the metal-type behaviour of simple Al-based crystals into a far more complex behaviour, with a fingerprint of semi-conductors that may be exploited in various applications, potential or realised. An account of the ones known to the author is given in the light of the relevant properties, namely light absorption, reduced adhesion and friction, heat insulation, reinforcement of composites for mechanical devices, and few more exotic ones. The role played by the search for applications of quasicrystals in the development of the field is briefly addressed in the concluding section. © 2012 The Royal Society of Chemistry.
Chaput L.,CNRS Jean Lamour Institute
Physical Review Letters | Year: 2013
The frequency dependent phonon Boltzmann equation is transformed to an integral equation over the irreducible part of the Brillouin zone. Simultaneous diagonalization of the collision kernel of that equation and a symmetry crystal class operator allow us to obtain a spectral representation of the lattice thermal conductivity valid at finite frequency. Combining this approach with density functional calculations, an ab initio dynamical thermal conductivity is obtained for the first time. The static thermal conductivity is also obtained as a particular case. The method is applied to C, Si, and Mg2Si and excellent agreement is obtained with the available static thermal conductivity measurements. © 2013 American Physical Society.
Henkel M.,CNRS Jean Lamour Institute
Nuclear Physics B | Year: 2013
Ageing phenomena far from equilibrium naturally present dynamical scaling and in many situations this may be generalised to local scale-invariance. Generically, the absence of time-translation-invariance implies that each scaling operator is characterised by two independent scaling dimensions. Building on analogies with logarithmic conformal invariance and logarithmic Schrödinger-invariance, this work proposes a logarithmic extension of local scale-invariance, without time-translation-invariance. Carrying this out requires in general to replace both scaling dimensions of each scaling operator by Jordan cells. Co-variant two-point functions are derived for the most simple case of a two-dimensional logarithmic extension. Their form is compared to simulational data for autoresponse functions in several universality classes of non-equilibrium ageing phenomena. © 2012 Elsevier B.V.
Allegra N.,CNRS Jean Lamour Institute
Nuclear Physics B | Year: 2015
In this work, some classical results of the pfaffian theory of the dimer model based on the work of Kasteleyn, Fisher and Temperley are introduced in a fermionic framework. Then we shall detail the bosonic formulation of the model via the so-called height mapping and the nature of boundary conditions is unravelled. The complete and detailed fermionic solution of the dimer model on the square lattice with an arbitrary number of monomers is presented, and finite size effect analysis is performed to study surface and corner effects, leading to the extrapolation of the central charge of the model. The solution allows for exact calculations of monomer and dimer correlation functions in the discrete level and the scaling behavior can be inferred in order to find the set of scaling dimensions and compare to the bosonic theory which predicts particular features concerning corner behaviors. Finally, some combinatorial and numerical properties of partition functions with boundary monomers are discussed, proved and checked with enumeration algorithms. © 2015 The Author.
Michot G.,CNRS Jean Lamour Institute
Acta Materialia | Year: 2011
Stress relaxation at a crack tip relies on the material's ability to generate dislocations. Despite the extensive literature devoted to crack-dislocation interaction, no one has yet explained how dislocations appear and multiply in order to build a fully plastic zone. Here we will show how a simple event, such as the intersection of a unique incoming dislocation with a crack front, induces the generation of new dislocations: this effect is called "stimulated emission". Submitted to the applied crack stress field, these dislocations can repeat the stimulation process step by step all along the crack front, through a cross-slip mechanism. Such a rapidly increasing rate of dislocations nucleation leads to a sudden growth of the plastic zone (avalanche). © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Chatelain C.,CNRS Jean Lamour Institute
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014
The q-state Potts model with long-range correlated disorder is studied by means of large-scale Monte Carlo simulations for q=2, 4, 8, and 16. Evidence is given of the existence of a Griffiths phase, where the thermodynamic quantities display an algebraic finite-size scaling, in a finite range of temperatures. The critical exponents are shown to depend on both the temperature and the exponent of the algebraic decay of disorder correlations, but not on the number of states of the Potts model. The mechanism leading to the violation of hyperscaling relations is observed in the entire Griffiths phase. © 2014 American Physical Society.
Dubois J.-M.,CNRS Jean Lamour Institute
Israel Journal of Chemistry | Year: 2011
For years, the community working on quasicrystals in many countries in the world was expecting the ultimate recognition of its contribution to the advancement of crystal chemistry, solid-state physics, mathematics, and other fields. Nearly thirty years after the initial discovery, it was finally awarded in October 2011 to Prof. Danny Shechtman by the Nobel Committee for Physics and Chemistry. Many, most often independent, achievements contributed to this success. The purpose of this article is to chronicle the role played by the applications of quasicrystals and related compounds in the development of the field and its financing by governmental institutions as well as private companies. Those applications, potential or realized, have made the field of quasicrystals comprehensible to the general public and to decision makers all over the world, including in Stockholm, in spite of its rather complicated high-dimensional crystallographic background, and in spite of the absolute opposition that a great chemist manifested against it in its infancy. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Collura M.,DellUniversity Pisa |
Karevski D.,CNRS Jean Lamour Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2014
We consider a quantum quench in a noninteracting fermionic one-dimensional field theory. The system of size L is initially prepared into two halves L ([-L/2,0]) and R ([0,L/2]), each of them thermalized at two different temperatures TL and TR, respectively. At a given time, the two halves are joined together by a local coupling and the whole system is left to evolve unitarily. For an infinitely extended system (L→), we show that the time evolution of the particle and energy densities is well described via a hydrodynamic approach which allows us to evaluate the correspondent stationary currents. We show, in such a case, that the two-point correlation functions are deduced, at large times, from a simple nonequilibrium steady state. Otherwise, whenever the boundary conditions are retained (in a properly defined thermodynamic limit), any current is suppressed at large times, and the stationary state is described by a generalized Gibbs ensemble, which is diagonal and depends only on the post-quench mode occupation. © 2014 American Physical Society.
Poncot M.,CNRS Jean Lamour Institute |
Addiego F.,CRP Henri Tudor |
Dahoun A.,CNRS Jean Lamour Institute
International Journal of Plasticity | Year: 2013
A model enabling the determination of the intrinsic mechanical constitutive equations of uniaxially stretched polymers is presented. This model takes into account the cavitation-induced volume strain which can occur during the deformation of such materials. In particular, the true intrinsic axial stress and strain depends on the overall volume strain and a form factor depicting the evolution of the voids shape. Based on our model, the true intrinsic behaviour of high-density polyethylene (HDPE), polypropylene/ethylene-propylene rubber (PP/EPR), and polyethylene terephtalate (PET) was assessed in tension. Compared to the overall true behaviour, the intrinsic true behaviour of the materials did not exhibit anomalies at large strain levels with changing experimental parameters (strain rate and temperature), and can be accurately predicted by means of phenomenological constitutive equations as the one proposed by G'sell and Jonas (1979). © 2012 Elsevier Ltd. All rights reserved.
Badreddine Assouar M.,Georgia Institute of Technology |
Oudich M.,CNRS Jean Lamour Institute
Applied Physics Letters | Year: 2011
Reliable numerical simulations of band structure for surface acoustic waves propagating in a two-dimensional phononic crystal are reported. Through an efficient finite element method and specific boundary conditions, a theoretical approach allowing a direct computation of surface acoustic wave's band structure for phononic crystal is proposed. Three types of phononic structures are investigated; fluid/solid, solid/solid, and air connected stubbed substrate. Using sound cone limitation, calculated results show the propagation of surface acoustic waves in the nonradiative region of the substrate. In addition, the modal displacements of the original guided surface modes supported by the studied structures are computed showing their original characteristics. © 2011 American Institute of Physics.