1,721,016 research outputs found
THERMOTRANSPORT COEFFICIENTS OF A CLASSICAL BINARY IONIC MIXTURE BY NONEQUILIBRIUM MOLECULAR-DYNAMICS
No full textThermotransport coefficients of a classical binary ionic mixture by non-equilibrium molecular dynamics
No full textThe authors present a non-equilibrium molecular dynamics (NEMD) computation of both direct and cross thermotransport coefficients of a strong coupled binary mixture of positive charges in a negative neutralising background (binary ionic mixture) in the special case in which the charge and mass ratios of the mobile species are the same. They use a modified version of the MacGowan-Evans NEMD algorithm. They find that the direct coefficients qualitatively agree with the predictions of the one-fluid approximation. The authors show that the cross properties depend mainly on the relative interaction energy of the two different species in the mixture, while the range of interaction gives a small correction
Isotopic shift of helium melting pressure: Path integral Monte Carlo study
No full textWe compute by a path integral Monte Carlo calculation the isotropic shift of helium melting pressure in the temperature range (T>100 K) where a discrepancy between theory and experiment has been recently reported. We use a realistic Aziz pair potential together with Bruch-McGee three-body forces for the interaction. The isotopic shift predicted in this work is in agreement with experiment; its measurement provides a good test of the interatomic potential of helium, as the isotopic shift is sensitive to the kinetic energy, which is determined by the short-range pair interaction. © 1994 The American Physical Society
A soft effective segment representation of semidilute polymer solutions
No full textA coarse-grained effective segment description of polymer solutions is presented, based on soft, transferable effective interactions between bonded and nonbonded effective segments. The number of segments is chosen such that the segment density does not exceed their overlap threshold, allowing polymer concentrations to be explored deep into the semidilute regime. This quantitative effective segment description is shown to preserve known scaling laws of polymer solutions and provides accurate estimates of amplitudes, while leading to a orders-of-magnitude increase in the simulation efficiency and allowing analytic calculations of structural and thermodynamic properties. © 2007 American Institute of Physics
Proceedings of the Europhysics Conference on Computational Physics 2004 - CCP 2004 - Preface
No full textPreface to the Conference Proceeding
COMPUTER PHYSICS COMMUNICATIONS Proceedings of the Europhysics Conference on Computational Physics 2004 (CCP 2004)
No full textThis volume contains the Proceedings of the Europhysics Conference on Computational Physics 2004, held in Genova, Italy, 1–4 September 2004
The normal, cryptorchid and retractile prepuberal human testis: a comparative morphometric ultrastructural study of 101 cases
No full textEnergy Gap Closure of Crystalline Molecular Hydrogen with Pressure
Full text linkWe study the gap closure with pressure of crystalline molecular hydrogen. The gaps are obtained from grand-canonical quantum Monte Carlo methods properly extended to quantum and thermal crystals, simulated by coupled electron ion Monte Carlo methods. Nuclear zero point effects cause a large reduction in the gap (∼2 eV). Depending on the structure, the fundamental indirect gap closes between 380 and 530 GPa for ideal crystals and 330-380 GPa for quantum crystals. Beyond this pressure the system enters into a bad metal phase where the density of states at the Fermi level increases with pressure up to ∼450-500 GPa when the direct gap closes. Our work partially supports the interpretation of recent experiments in high pressure hydrogen
Characterization of molecular-atomic transformation in fluid hydrogen under pressure via long-wavelength asymptote of charge density fluctuations
No full textWe report the observation of a pressure-induced non-monotonic behavior of the long-wavelength asymptote of total charge density fluctuations right in the region of molecular-to-atomic fluid transformation from ab-initio molecular dynamics (AIMD) simulations of fluid hydrogen. Screening in the total charge density composed of point protons and distribution of electronic density is studied within density functional theory (DFT) via total charge-charge static structure factor SQQDFT(k). We show from theory and AIMD that the long-wavelength behavior of SQQDFT(k → 0) ~ kη with η = 4 in neutral atomic and in fully metallic liquids, while η = 2 is in an ionic mixture with long-range Coulomb interaction. At high temperature (2500 K) we find a change in η with density around the region of molecular dissociation. At lower temperature (1000 K, below the critical point), we observe an η value different from 4 only in the pressure vs. density plateau region. This observation is consistent with a smooth molecular to atomic transformation, and implies existence of a semiconducting state with some unscreened protons responsible for long-range interaction
Entropic self-assembly of diblock copolymers into disordered and ordered micellar phases
No full textWe investigate the self-assembly of an athermal model of AB diblock copolymers into disordered and ordered micellar microphases. The original microscopic lattice model with ideal A strands and self-avoiding B strands is mapped onto a system of ultrasoft dumbbells, with monomer-averaged effective interactions between the centers of mass (CMs) of the two blocks. Extensive Monte Carlo simulations of this coarse-grained model are reported for several length ratios f ) L A/( L A + L B) of the two strands of lengths L A and L B. Clear-cut evidence is found for clustering and self-assembly into micelles with a mean aggregation number of n ≃ 100 beyond a critical micellar concentration (cmc) in the semidilute regime. The cmc is found to decrease with increasing f , as predicted by an analytic calculation based on the random phase approximation. The initially disordered dispersion of polydisperse spherical micelles undergoes a disorder-order transition to a micellar crystal phase at higher copolymer concentrations. The effective pair potential between the micellar CMs is determined by inverting the measured CM-CM pair distribution function and is found to become steeper with increasing density. © 2009 American Chemical Society
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