The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Christopher M. Sorensen - One of the best experts on this subject based on the ideXlab platform.
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Structure Factor scaling in colloidal phase separation.
Physical Review E, 2004Co-Authors: Juan J. Cerdà, Christopher M. Sorensen, Tomàs Sintes, Amitabha ChakrabartiAbstract:The dynamical scaling hypothesis for the Structure Factor, S (q) , in depletion-driven colloidal phase separation is studied by carrying out Brownian dynamics simulations. A true dynamical scaling is observed for shallow quenches into the two-phase coexistence region. In such a quench, compact clusters nucleate and grow with time and there is only one characteristic length scale in the system after an initial transient period. Scaling is satisfied beyond this initial period. In contrast, deep quenches lead to fractal cluster growth, and the system is controlled by two characteristic lengths that evolve differently in time [Huang, Oh, and Sorensen (HOS), Phys. Rev. E 57, 875 (1998)]. True dynamical scaling thus cannot be expected to hold. However, an apparent scaling for the Structure Factor is observed over some period of time when these two characteristic length scales become comparable to each other. We compare our simulation results for the total Structure Factor to theoretical predictions by HOS by writing it as a product of cluster-cluster and the averaged single-cluster Structure Factors, each with its own characteristic length.
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Structure Factor SCALING IN AGGREGATING SYSTEMS
Physical Review E, 1998Co-Authors: H. Huang, Christopher M. SorensenAbstract:We study the Structure Factor of evolving two-phase systems such as aggregating colloids and spinodally decomposing fluids. We interpret the total Structure Factor as described well by the product of cluster-cluster and single-cluster Structure Factors, each with their own characteristic length, the mean cluster nearest-neighbor separation, and the cluster size, respectively. Both length scales are thus relevant to the total Structure Factor. For systems with moderate to strong cluster-cluster correlations, this product causes an apparent peak in the Structure Factor. For compact clusters, i.e., clusters with a fractal dimension equal to the spatial dimension, this peak obeys the experimentally observed scaling law. However, for fractal clusters the two length scales evolve differently, hence scaling cannot occur. Despite this, our simulations show an apparent scaling when the system is dense enough so that the two length scales are comparable in magnitude. When this occurs, each length scale eliminates the individual effect of the other from the total Structure Factor leaving a peak. These results explain both the lack of scaling early and the scaling observed latter in experiments on aggregating colloids. An important conclusion is that the position of this peak ${q}_{m}$ does not represent a true length scale of the system.
Sandro Stringari - One of the best experts on this subject based on the ideXlab platform.
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dynamic Structure Factor and momentum distribution of a trapped bose gas
Physical Review A, 2000Co-Authors: Federico Zambelli, D M Stamperkurn, Lev P. Pitaevskii, Sandro StringariAbstract:The dynamic Structure Factor of a trapped Bose-Einstein condensed gas is investigated at zero temperature in the framework of Bogoliubov theory. Different values of momentum transfer are considered, ranging from the phonon to the single-particle regime. Various approximate schemes are discussed, including the local density approximation, where the system is locally described as a uniform gas, and the impulse approximation, in which the response is fixed by the momentum distribution of the condensate. A comprehensive approach, based on the eikonal expansion, is presented. The predictions of theory are successfully compared with the results of recent two-photon Bragg scattering experiments, at both low and high momentum transfer. Relevant features of the dynamic Structure Factor are also discussed using the formalism of sum rules and the concept of scaling. Particular emphasis is given to the regime of high momentum transfer, in which the dynamic Structure Factor is sensitive to the behavior of the order parameter in momentum space, and some instructive examples showing the consequence of long-range coherence are presented.
Otto Glatter - One of the best experts on this subject based on the ideXlab platform.
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small angle scattering of interacting particles ii generalized indirect fourier transformation under consideration of the effective Structure Factor for polydisperse systems
Journal of Applied Crystallography, 1999Co-Authors: B Weyerich, J Brunnerpopela, Otto GlatterAbstract:The indirect Fourier transformation (IFT) is the method of choice for the model-free evaluation of small-angle scattering data. Unfortunately, this technique is only useful for dilute solutions because, for higher concentrations, particle interactions can no longer be neglected. Thus an advanced technique was developed as a generalized version, the so-called generalized indirect Fourier transformation (GIFT). It is based on the simultaneous determination of the form Factor, representing the intraparticle contributions, and the Structure Factor, describing the interparticle contributions. The former can be determined absolutely free from model assumptions, whereas the latter has to be calculated according to an adequate model. In this paper, various models for the Structure Factor are compared, e.g. the effective Structure Factor for polydisperse hard spheres, the averaged Structure Factor, the local monodisperse approximation and the decoupling approximation. Furthermore, the Structure Factor for polydisperse rod-like particles is presented. As the model-free evaluation of small-angle scattering data is an essential point of the GIFT technique, the use of a Structure Factor without any influence of the form amplitude is advisable, at least during the first evaluation procedure. Therefore, a series of simulations are performed to check the possibility of the representation of various Structure Factors (such as the effective Structure Factor for hard spheres or the Structure Factor for rod-like particles) by the less exact but much simpler averaged Structure Factor. In all the observed cases, it was possible to recover the exact form Factor with a free determined parameter set for the Structure Factor. The resulting parameters of the averaged Structure Factor have to be understood as apparent model parameters and therefore have only limited physical relevance. Thus the GIFT represents a technique for the model independent evaluation of scattering data with a minimum of a priori information.
Brayden Ware - One of the best experts on this subject based on the ideXlab platform.
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anomalous relaxation and the high temperature Structure Factor of xxz spin chains
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Sarang Gopalakrishnan, Romain Vasseur, Brayden WareAbstract:We compute the spin-Structure Factor of XXZ spin chains in the Heisenberg and gapped (Ising) regimes in the high-temperature limit for nonzero magnetization, within the framework of generalized hydrodynamics, including diffusive corrections. The Structure Factor shows a hierarchy of timescales in the gapped phase, owing to s-spin magnon bound states (“strings”) of various sizes. Although short strings move ballistically, long strings move primarily diffusively as a result of their collisions with short strings. The interplay between these effects gives rise to anomalous power-law decay of the spin-Structure Factor, with continuously varying exponents, at any fixed separation in the late-time limit. We elucidate the cross-over to diffusion (in the gapped phase) and to superdiffusion (at the isotropic point) in the half-filling limit. We verify our results via extensive matrix product operator calculations.
Ronald Redmer - One of the best experts on this subject based on the ideXlab platform.
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Ab initio simulations for the ion-ion Structure Factor of warm dense aluminum.
Physical Review Letters, 2014Co-Authors: Hannes R. Rüter, Ronald RedmerAbstract:We perform ab initio simulations based on finite-temperature density functional theory in order to determine the static and dynamic ion-ion Structure Factor in aluminum. We calculate the dynamic Structure Factor via the intermediate scattering function and extract the dispersion relation for the collective excitations. The results are compared with available experimental x-ray scattering data. Very good agreement is obtained for the liquid metal domain. In addition we perform simulations for warm dense aluminum in order to obtain the ion dynamics in this strongly correlated quantum regime. We determine the sound velocity for both liquid and warm dense aluminum which can be checked experimentally using narrow-bandwidth free electron laser radiation.
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Equation of state and Structure Factor of mercury
Journal of Non-Crystalline Solids, 1996Co-Authors: Stefan Nagel, Ronald Redmer, Gerd RöpkeAbstract:Abstract A quantum statistical approach is utilized to give a unified treatment of the metal-non-metal and liquid-vapour transition in expanded mercury. An equation of state is proposed with respect to thermodynamic stability. The resulting coexistence curve and the location of the critical point are in good agreement with experimental data. The static Structure Factor is calculated along the coexistence line within the MHNC approximation. The limiting cases of the metallic liquid and the insulating vapour are treated by an effective ion-ion interaction potential derived within the nearly free electron model and a Lennard-Jones potential, respectively. The resulting Structure Factors are compared with experiments.
