ORBi Collection: Physics
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Nanosession: Multiferroic Thin Films and Heterostructures
http://hdl.handle.net/2268/186396
Title: Nanosession: Multiferroic Thin Films and Heterostructures
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<br/>Author, coauthor: Burton, J. D.; Yin, J; Li, X. G.; Kim, Y.M.; Borisevich, A. Y.; Li, Q.; Tsymbal, E. Y.; Pantel, D.; Goetze, S.; Alexe, M.; Hesse, D.; Geprägs, S; Opel, M; Goennenwein, S T B; Gross, R; Zanolli, Zeila; Wojdel, J C; Iniguez, J; Ghosez, Philippe; Glavic, A; Voigt, J; Schierle, E; Weschke, E; Brückel, T; Fontcuberta, J; Fina, I; Fàbrega, L; Martí, X; Sánchez, F; Lorenz, M; Ziese, M; Wagner, G; Esquinazi, P; Grundmann, M
<br/>
<br/>Abstract: This chapter presents the theoretical and experimental evidence of a novel magnetoelectric mechanism producing a giant resistive switching effect at the interface between a ferroelectric perovskite oxide, BaTiO3 (BTO), and a complex oxide manganite electrode, La1xSrxMnO3. It presents a detailed study of the magnetic properties of multiferroic hybrid systems consisting of BTO as the ferroelectric and Ni or Fe3O4 as the ferromagnetic layers. The chapter discusses the possibility of achieving electric control of the magnetization, possibly at room temperature, through a specific (trilinear) coupling of the polarization with two other nonpolar lattice instabilities which occurs in the socalled hybrid improper ferroelectrics. Firstprinciples modelling techniques are used to investigate a promising system: BiFeO3/LaFeO3 superlattice. It presents the investigation of the multiferroic properties in TbMnO3 thin films with soft Xray resonant magnetic scattering (XRMS) performed at the UE46PGM1 beamline of BESSY II.
Thu, 01 Oct 2015 14:13:03 GMT

Multifractality of quantum wave functions in the presence of perturbations
http://hdl.handle.net/2268/186352
Title: Multifractality of quantum wave functions in the presence of perturbations
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<br/>Author, coauthor: Dubertrand, Rémy; GarciaMata, Ignacio; Georgeot, Bertrand; Giraud, Olivier; Lemarié, Gabriel; Martin, John
<br/>
<br/>Abstract: We present a comprehensive study of the destruction of quantum multifractality in the presence of perturbations. We study diverse representative models displaying multifractality, including a pseudointegrable system, the Anderson model, and a random matrix model. We apply several types of natural perturbations which can be relevant for experimental implementations. We construct an analytical theory for certain cases and perform extensive largescale numerical simulations in other cases. The data are analyzed through refined methods including double scaling analysis. Our results confirm the recent conjecture that multifractality breaks down following two scenarios. In the first one, multifractality is preserved unchanged below a certain characteristic length which decreases with perturbation strength. In the second one, multifractality is affected at all scales and disappears uniformly for a strongenough perturbation. Our refined analysis shows that subtle variants of these scenarios can be present in certain cases. This study could guide experimental implementations in order to observe quantum multifractality in real systems.
Wed, 30 Sep 2015 12:56:37 GMT

Maximal fidelity between symmetric multiqubit states and entanglement classes
http://hdl.handle.net/2268/186303
Title: Maximal fidelity between symmetric multiqubit states and entanglement classes
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<br/>Author, coauthor: Neven, Antoine; Mathonet, Pierre; Gühne, Otfried; Bastin, Thierry
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<br/>Abstract: We present the results of our research concerning a conjecture about the maximal fidelity between a symmetric (permutation invariant) multiqubit
state and the states belonging to a given entanglement class.
Tue, 29 Sep 2015 13:31:20 GMT

The onset, evolution and magnetic braking of vortex lattice instabilities in nanostructured superconducting films
http://hdl.handle.net/2268/186132
Title: The onset, evolution and magnetic braking of vortex lattice instabilities in nanostructured superconducting films
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<br/>Author, coauthor: Adami, ObaïdAllah; Jelic, Zeljko; Xue, Cun; AbdelHafiez, Mahmoud; Hackens, Benoit; Moshchalkov, Victor V.; Milosevic, Milorad V.; Van de Vondel, Joris; Silhanek, Alejandro
<br/>
<br/>Abstract: In 1976 Larkin and Ovchinnikov [Sov. Phys. JETP 41, 960 (1976)] predicted that vortex matter
in superconductors driven by an electrical current can undergo an abrupt dynamic transition from a fluxflow regime to a more dissipative state at suficiently high vortex velocities. Typically this transition manifests itself as a large voltage jump at a particular current density, socalled instability current density J, which is smaller than the depairing current. By tuning the effective pinning strength in Al fi lms, using an artifi cial periodic pinning array of triangular holes, we show that a unique and well defi ned instability current density exists if the pinning is strong, whereas a series of multiple voltage transitions appear in the relatively weaker pinning regime. This behavior is consistent with timedependent GinzburgLandau simulations, where the multiplestep transition can be unambiguously attributed to the progressive development of vortex chains and subsequently phaseslip lines. In addition, we explore experimentally the magnetic braking e ffects, caused by a thick Cu layer deposited on top of the superconductor, on the instabilities and the vortex ratchet effect.
Wed, 23 Sep 2015 07:06:06 GMT

Abinitio calcualtion of spindependent transport quantities in disordered materials
http://hdl.handle.net/2268/186075
Title: Abinitio calcualtion of spindependent transport quantities in disordered materials
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<br/>Author, coauthor: Di Gennaro, Marco
Mon, 21 Sep 2015 09:10:23 GMT

The lightfront gaugeinvariant energymomentum tensor
http://hdl.handle.net/2268/186006
Title: The lightfront gaugeinvariant energymomentum tensor
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<br/>Author, coauthor: Lorce, Cédric
Wed, 16 Sep 2015 11:38:41 GMT

Spinorbit correlations in the nucleon
http://hdl.handle.net/2268/186005
Title: Spinorbit correlations in the nucleon
<br/>
<br/>Author, coauthor: Lorce, Cédric
Wed, 16 Sep 2015 11:27:26 GMT

Gauge symmetry and background independence: Should the proton spin decomposition be path independent?
http://hdl.handle.net/2268/186004
Title: Gauge symmetry and background independence: Should the proton spin decomposition be path independent?
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<br/>Author, coauthor: Lorce, Cédric
Wed, 16 Sep 2015 11:16:18 GMT

Coherence and manybody effects in the transport of Bose–Einstein condensates
http://hdl.handle.net/2268/185909
Title: Coherence and manybody effects in the transport of Bose–Einstein condensates
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<br/>Author, coauthor: Dujardin, Julien
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<br/>Abstract: This thesis presents investigations on the interplay of coherence and manybody effects in the quasi onedimensional transport of BoseEinstein condensates (BEC) through scattering potentials. Such configurations can be realized with guided atom lasers that provide a coherent atomic beam. An exact theoretical description of the dynamics is out of reach due to the presence atomatom interactions. Different levels of approximations are nevertheless possible with their strengths and weaknesses. The meanfield approximation, where the dynamics of the BEC is governed by the GrossPitaevskii equation, is most commonly used in the field of ultracold atoms.
In this thesis the truncated Wigner method is used to go beyond the standard GrossPitaevskii description. This method is adapted in order to study the scattering of BoseEinstein condensates in onedimensional waveguides where atomatom interactions and external potentials are nonvanishing only in a finite region of space. In this case, the truncated Wigner method is combined with the smooth exterior complex scaling method and incorporates quantum noise that originate from the vacuum fluctuations in the waveguide. Inelastic scattering is shown to play a major role in the resonant transport of BEC through a symmetric double potential barrier effectively forming an atomic quantum dot. Indeed, fully resonant transmission is prohibited and incoherent atoms as well as collective oscillations are detected in the transmitted beam. It is also shown that inelastic scattering destroys Anderson localization in the case of transport through disordered potentials. The classical (incoherent) ohmic transmission is recovered for finite atomatom interactions.
The validity of the truncated Wigner method is then assessed using the semiclassical van VleckGutzwiller propagator in the Fock space of the manybody system. It is shown that the truncated Wigner method corresponds to the socalled diagonal approximation, and it is possible to identify the leading correction to the truncated Wigner results, which is provided by the socalled coherent backscattering (CBS) contribution. Coherent basckattering in Fock space is a genuine quantum manybody effect that lies beyond the reach of any meanfield approach. For the case of closed BoseHubbard models, the relevance of CBS is confirmed by numerically comparing the (classical) truncated Wigner evolution probabilities to the exact quantum probabilities in BoseHubbard models: While a CBSinduced enhancement of the return probability to the initial state is clearly seen in the exact quantum simulations of the bosonic manybody system, this enhancement is absent in the classical calculations. The magnitude and dependence of the CBS contribution on gauge fields, which break timereversal invariance, is numerically confirmed. For the case of disordered open systems, it can be shown that this contribution as well as nextto leading order contributions vanish thereby confirming the validity of the truncated Wigner method.; Cette thèse présente les investigations réalisées sur la relation entre les effets à plusieurs corps et la coherence lors de phénomènes de transport quasiunidimensionels de condensats de BoseEinstein (CBE) à travers divers potentiels de diffusion. De telles configurations peuvent être réalisées avec des lasers à atomes qui créent des faisceaux coherents de matière. Une description exacte de la dynamique à plusieurs corps est hors de portée à cause des interactions entre atomes. Malgré tout, différents niveaux d'approximation sont possibles, chacun possédant leurs forces et faiblesses. L'approximation en champ moyen, où la dynamique du CBE est régie par l'équation de GrossPitaevskii, est la plus utilisée dans le domaine des atomes ultrafroids.
Dans cette thèse, la méthode de Wigner tronquée, qui est une amélioration de la description fournie par l'équation de GrossPitaevskii, est utilisée. Cette méthode est adaptée pour l'étude de la diffusion de condensats de BoseEinstein dans des guides d'ondes unidimensionels où les interactions entre atomes et les potentiels extérieurs ont un support fini. Dans ce cas, la méthode de Wigner tronquée est combinée avec la méthode de dilatation complexe extérieure lissée (smooth exterior complex scaling) et avec du bruit quantique, provenant des fluctuations quantiques dans le guide d'onde. Les effets, non négligeables, des collisions inélastiques sont mis en évidence lors du transport résonnant d'un CBE à travers une double barrière de potentiel symétrique formant un point quantique. En effet, une transmission résonnante parfaite est prohibée et des atomes incoherents ainsi que des oscillations collectives sont détectées dans le faisceau atomique transmis. Il est aussi démontré que la diffusion inélastique est responsable de la destruction de la localisation d'Anderson dans le cas du transport à travers des potentiels désordonnés. Une transmission ohmique (incohérente) est retrouvée pour des interactions finies entre atomes.
La validité de la méthode de Wigner tronquée est évaluée en utilisant le propagateur semiclassique de van VleckGutzwiller dans l'espace de Fock du sytème à plusieurs corps. Il est démontré que la méthode de Wigner tronquée correspond à l'approximation diagonale et qu'il est possible d'identifier la correction dominante appellée rétrodiffusion cohérente. La rétrodiffusion cohérente dans l'espace de Fock est un effet à plusieurs corps purement quantique et ne peut être reproduite par aucune théorie en champ moyen.
L'analyse numérique des probabilités de transitions quantiques pour des systèmes de BoseHubbard confirme la présence de rétrodiffusion cohérente alors qu'elle est absente pour des simulations utilisant la méthode (classique) de Wigner tronquée. L'amplitude ainsi que la dépendance visàvis d'un champ de jauge de la contribution de rétrodiffusion cohérente est confirmée numériquement. Dans le cas de systèmes ouverts désordonnés, il a été montré que la rétrodiffusion cohérente ainsi que les corrections d'ordre supérieur sont inexistantes, confirmant la validité de la méthode de Wigner tronquée.
Tue, 15 Sep 2015 07:17:41 GMT

Direct Numerical Simulation of Mixed Convection in Turbulent Channel Flow: On the Reynolds number dependency of momentum and heat transfer under unstable stratification
http://hdl.handle.net/2268/185877
Title: Direct Numerical Simulation of Mixed Convection in Turbulent Channel Flow: On the Reynolds number dependency of momentum and heat transfer under unstable stratification
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<br/>Author, coauthor: Sid, Samir; Dubief, Yves; Terrapon, Vincent
<br/>
<br/>Abstract: Direct numerical simulations of unstably stratified turbulent channel flow have been performed in order to investigate the Reynolds number effect on mixed convection. Six different cases are considered with friction Reynolds number Re_\tau =180 and 395 and friction Richardson number Ri_\tau = 0, 100 and 1000. It is shown that both friction coefficient and Nusselt number increase under unstable stratification for a sufficiently large Richardson number. At low Richardson number, the friction coefficient can either increase or decrease depending on the Reynolds number. The drag reduction is associated with an increase of mean velocity due to an enhanced dissipation of Reynolds shear stress by pressure strain in the buffer region. The breakdown of the Reynolds analogy is demonstrated as the turbulent Prandtl number exhibits a nonconstant behavior due to buoyancy.
Mon, 14 Sep 2015 04:34:14 GMT

A zigzag antiferromagnetic quantum ground state in monoclinic honeycomb lattice antimonates A3Ni2SbO6 (A=Li, Na)
http://hdl.handle.net/2268/185845
Title: A zigzag antiferromagnetic quantum ground state in monoclinic honeycomb lattice antimonates A3Ni2SbO6 (A=Li, Na)
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<br/>Author, coauthor: Zvereva, E.A.; Stratan, M.I.; Ovchenkov, Y.A.; Nalbandyan, V.B.; Lin, J.Y.; Vavilova, E.L.; Iakovleva, M.F.; AbdelHafiez, M.; Silhanek, Alejandro; Chen, X.J.; Stroppa, A.; Picozzi, S.; Jeschke, H.O.; Valentí, R.; Vasiliev, A.N.
<br/>
<br/>Abstract: We present a comprehensive experimental and theoretical study of the electronic and magnetic properties of two quasitwodimensional (2D) honeycomblattice monoclinic compounds A3Ni2SbO6 (A=Li, Na). Magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic (AFM) long range order at low temperatures with Néel temperatures ~ 14 and 16 K for Li3Ni2SbO6 and Na3Ni2SbO6, respectively. The effective magnetic moments of 4.3 Bohr magnetons/f.u. (Li3Ni2SbO6) and 4.4 Bohr magnetons/f.u. (Na3Ni2SbO6) indicate that Ni2+ is in a highspin configuration (S=1). The temperature dependence of the inverse magnetic susceptibility follows the CurieWeiss law in the hightemperature region and shows positive values of the Weiss temperature ~ 8 K (Li3Ni2SbO6) and ~12 K (Na3Ni2SbO6) pointing to the presence of nonnegligible ferromagnetic interactions, although the system orders AFM at low temperatures. In addition, the magnetization curves reveal a fieldinduced (spinflop type) transition below TN that can be related to the magnetocrystalline anisotropy in these systems. These observations are in agreement with density functional theory calculations, which show that both antiferromagnetic and ferromagnetic intralayer spin exchange couplings between Ni2+ ions are present in the honeycomb planes supporting a zigzag antiferromagnetic ground state. Based on our experimental measurements and theoretical calculations we propose magnetic phase diagrams for the two compounds.
Fri, 11 Sep 2015 14:40:24 GMT

Soutien télématique à la résolution de problèmes en physique en première année de bachelier
http://hdl.handle.net/2268/185804
Title: Soutien télématique à la résolution de problèmes en physique en première année de bachelier
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<br/>Author, coauthor: Marique, PierreXavier
<br/>
<br/>Abstract: Présentation d'un projet de soutien à l'enseignement proposé aux étudiants éprouvant des difficultés en résolution de problèmes de physique.; Presentation of a learning support project for students experiencing difficulties in solving physics problems
Thu, 10 Sep 2015 13:25:13 GMT

Intramolecular vibrational relaxation seen as expansion in phase space. III. The longtime limit
http://hdl.handle.net/2268/185797
Title: Intramolecular vibrational relaxation seen as expansion in phase space. III. The longtime limit
<br/>
<br/>Author, coauthor: PavlovVerevkin, V. B.; Lorquet, JeanClaude
<br/>
<br/>Abstract: Asymptotic formulas that describe the behavior of the function N(T) measuring the phase space volume sampled by a nonstationary wave packet during its time evolution are derived. It is shown that, in the longtime limit, N(T)∼T1 when the dynamics is regular, whereas N(T)∼T2 In T for the chaotic case. © 1997 American Institute of Physics.
Thu, 10 Sep 2015 09:46:59 GMT

Abinitio study of thermoelectricity of layered tellurium compounds
http://hdl.handle.net/2268/185792
Title: Abinitio study of thermoelectricity of layered tellurium compounds
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<br/>Author, coauthor: Ibarra Hernández, Wilfredo
<br/>
<br/>Abstract: In this thesis, we explore the electronic, dynamic and thermoelectric properties
of different telluriumbased compounds. We perform abinitio calculations
within the Vienna Abinitio Simulation Package (VASP) that works in
the framework of Density Functional Theory (DFT). For the thermoelectric
properties, we use the Boltztrap code that solves the Boltzmann Transport
Equations (BTE) for electrons within the Constant Relaxation Time Approximation
(CRTA). This computational package allows us to obtain accurate
values of the Seebeck coefficient as a function of temperature and carrier concentration
(this last with the help of the rigid band approximation). While
for the calculation of the lattice contribution to the thermal conductivity, we
use the ShengBTE code that solves the BTE for phonons iteratively. The first telluriumbased compound that we study is the best room temperature
thermoelectric material, Bi2Te3. We obtain results comparable with
experimental data for the Seebeck coefficient at room temperature and pressure.
Afterwards, we proceed to explore the evolution of the electronic properties
and the thermoelectric performance under pressures up to 5 GPa. We
reproduce the overall trend of the Seebeck coefficient as a function of pressure
for two different values of doping, however, our results do not reproduce the
small improvement found in experiments close to 1 GPa. Nevertheless, we
support the experimental evidence of an Electronic Topological Transition
(ETT) around 2 GPa and we explain this particular behavior. We also perform calculations on the telluriumbased phasechange materials
(GeTe)x(Sb2Te3)1 (with x = 1, 2, 3). We show results for different
stacking configurations since for some compositions, the stacking arrangement
of the atoms in the primitive cell is still unsettled. We find that the
change of the atomic arrangement leads to the systems to go from semiconductors
to metals. We find that the semiconductor arrangements systematically
overestimate the experimental values for the Seebeck coefficient,
whereas the metallic stacking sequences are in very good agreement with the experimental data for the Seebeck coefficient and for the lattice contribution
to the thermal conductivity. We show that (GeTe)x(Sb2Te3)1 materials could
reach values of ZT=0.5 around 600 K with a proper optimization of S with
respect to the carrier concentration. We also report that in the case of x=3,
the most accepted stacking configuration is dynamically unstable, therefore
we proposed another sequence. Finally, we discuss the discrepancies between
our work and recent theoretical reports that claim the existence of a Diraccone
like band structure for (GeTe)2(Sb2Te3)1. We explain the conditions
necessary to obtain such electronic topology.
Thu, 10 Sep 2015 08:38:58 GMT

Intramolecular vibrational relaxation seen as expansion in phase space. 4. Generic relaxation laws for a spectroscopic clump profile
http://hdl.handle.net/2268/185763
Title: Intramolecular vibrational relaxation seen as expansion in phase space. 4. Generic relaxation laws for a spectroscopic clump profile
<br/>
<br/>Author, coauthor: PavlovVerevkin, V. B.; Lorquet, JeanClaude
<br/>
<br/>Abstract: We examine the volume of phase space sampled by a nonstationary wave packet when the spectral function consists of a single clump or of a series of them. The relaxation laws are expressed in terms of reduced time variables tau, whose definition involves either the average density of states (for a single clump) or appropriately weighted average densities of states (when the spectrum consists of many clumps). Introducing reasonable approximations, very simple generic relaxation laws are derived for the ratio N(tau)/Ninfinity which measures the fraction of available phase space that has been sampled by time tau. Under certain assumptions, these laws are found to depend neither on the number nor on the individual features (shapes and widths) of the clumps. However, they strongly depend on the nature (regular or chaotic) of the underlying dynamics. When the dynamics is regular, the relaxation law is expressed in terms of tau(1), whereas the corresponding equation in the chaotic limit is slightly more complicated and involves terms in tau(2) and tau(2) ln tau. Phase space is thus explored according to essentially different relaxation laws in the regular and chaotic limits, the difference being appreciable during the entire relaxation. These laws reflect in the time domain the difference in the distribution of nearestneighbor level spacings observed in the energy domain (Poisson or Wigner statistics).
Wed, 09 Sep 2015 13:50:50 GMT

Dynamical constraints and adiabatic invariants in chemical reactions
http://hdl.handle.net/2268/185762
Title: Dynamical constraints and adiabatic invariants in chemical reactions
<br/>
<br/>Author, coauthor: Lorquet, JeanClaude
<br/>
<br/>Abstract: For longrange electrostatic potentials and, more generally, when the topography of the potential energy surface is locally simple, the reaction path coordinate is adiabatically separable from the perpendicular degrees of freedom. For the ionpermanent dipole and ionquadrupole interactions, the Poisson bracket of the adiabatic invariant decreases with the interfragment distance more rapidly than the electrostatic potential. The smaller the translational momentum, the moment of inertia of the neutral fragment, and the dipole or quadrupole moments are, the more reliable the adiabatic approximation is, as expected from the usual argumentation. Closedform expressions for an effective onedimensional potential in an adiabatic Hamiltonian are given. Connection with a model where the decoupling is exact is obtained in the limit of an infinitely heavy dipole. The dynamics is also constrained by adiabatic invariance for a harmonic valley about a curved reaction path, as shown by the reaction path Hamiltonian method. The maximum entropy method reveals that, as a result of the invariance properties of the entropy, constraints whose validity has been demonstrated locally only subsist in all parts of phase space. However, their form varies continuously, and they are not necessarily expressed in simple terms as they are in the asymptotic region. Therefore, although the influence of adiabatic invariance has been demonstrated at asymptotically large values of the reaction coordinate only, it persists in more interesting ranges.
Wed, 09 Sep 2015 13:46:37 GMT

Optimization of Thermoelectric Properties of MgAgSbBased Materials: A FirstPrinciples Investigation
http://hdl.handle.net/2268/185729
Title: Optimization of Thermoelectric Properties of MgAgSbBased Materials: A FirstPrinciples Investigation
<br/>
<br/>Author, coauthor: Miao, Naihua; Ghosez, Philippe
<br/>
<br/>Abstract: Recently, MgAgSbbased materials (MAS) have been proposed as promising candidates for roomtemperature thermoelectric applications with a ZT larger than unity. In this work, we present a comprehensive theoretical study of the structural, electronic, and thermoelectric properties of MAS by combining firstprinciples calculations and Boltzmann transport theory. The predicted Seebeck coefficients are compared with available experimental data. The effects of crystal structure and volume on the electronic and thermoelectric properties of MAS are discussed. The thermoelectric quantities are optimized with respect to the chemical potential tuned by doping carriers. It is suggested that the thermoelectric performance of the α phase of MAS can be enhanced by hole doping and strain engineering. Our work intends to provide a theoretical support for future improvement on the thermoelectric performance of MAS and related materials.
Wed, 09 Sep 2015 07:36:03 GMT

FirstPrinciples Study on the Lattice Dynamics and Thermoelectric Properties of Materials
http://hdl.handle.net/2268/185720
Title: FirstPrinciples Study on the Lattice Dynamics and Thermoelectric Properties of Materials
<br/>
<br/>Author, coauthor: Miao, Naihua
<br/>
<br/>Abstract: Thermoelectricity has been regarded as one of the most promising strategies for clean, lowcost and environmental friendly sustainable energy for several decades. Perovskite oxides, like SrRuO3, are considered as a potential thermoelectric material for lowcost and largescale thermoelectric applications due to their good thermal and chemical stability in a wide temperature range, great flexibility for structural and compositional manipulating, and environmental friendliness. This thesis is devoted to a theoretical study of the lattice dynamics and thermoelectric properties of materials, like SrRuO3 perovskite and MgAgSbbased materials. Firstly, to obtain insight into the lattice dynamics of the SrRuO3, the phononrelated properties are presented and contributes to rationalize better why many ABO3 perovskites, including metallic compounds, exhibit an orthorhombic ground state. Then the thermoelectric properties of SrRuO3 are investigated by combining firstprinciples calculations and Boltzmann transport theory, revealing the relationship between the exchangecorrelation functionals and the thermoelectric quantities. Furthermore, based on the firstprinciples calculations, effective model potentials for SrRuO3 are constructed providing access to the finitetemperature properties and phasetransitions. Additionally, the electronic structure and thermoelectric properties of a class of new emerging MgAgSbbased materials, which are promising for roomtemperature thermoelectric applications, are also studied and the optimization strategies are proposed for the improvement of thermoelectric performance.
Tue, 08 Sep 2015 15:29:08 GMT

Adiabatic invariance along the reaction coordinate
http://hdl.handle.net/2268/185671
Title: Adiabatic invariance along the reaction coordinate
<br/>
<br/>Author, coauthor: Lorquet, JeanClaude
<br/>
<br/>Abstract: In a twodimensional space where a point particle interacts with a diatomic fragment, the action integral Φ pθ dθ (where θ is the angle between the fragment and the line of centers and pθ its conjugate momentum) is an adiabatic invariant. This invariance is thought to be a persistent dynamical constraint. Indeed, its classical Poisson bracket with the Hamiltonian is found to vanish in particular regions of the potential energy surface: asymptotically, at equilibrium geometries, saddle points, and inner turning points, i.e., at remarkable situations where the topography of the potential energy surface is locally simple. Studied in this way, the adiabatic decoupling of the reaction coordinate is limited to disjoint regions. However, an alternative view is possible. The invariance properties of entropy (as defined in information theory) can be invoked to infer that dynamical constraints that are found to operate locally subsist everywhere, throughout the entire reactive process, although with a modified expression. © 2009 American Institute of Physics.
Mon, 07 Sep 2015 14:48:09 GMT

Infrared holographic interferometry for metrology of space payloads and NDI by optical‐laser techniques for aeronautical composites
http://hdl.handle.net/2268/185617
Title: Infrared holographic interferometry for metrology of space payloads and NDI by optical‐laser techniques for aeronautical composites
<br/>
<br/>Author, coauthor: Georges, Marc
Sun, 06 Sep 2015 12:06:47 GMT