Search results for "classical"

Measurement of the self-intermediate scattering function of suspensions of hard spherical particles near the glass transition

1998

Dynamic light-scattering measurements are reported for suspensions at concentrations in the vicinity of the glass transition. In a mixture of identically sized but optically different particles having hard-sphere-like interactions, we project out the incoherent (or self-) intermediate scattering functions by adjusting the refractive index of the suspending liquid until scattering from the structure is suppressed. Due to polydispersity, crystallization is sufficiently slow so that good estimates of ensemble-averaged quantities can be measured for the metastable fluid states. Crystallization of the suspensions is still exploited, however, to set the volume fraction scale in terms of effective…

Nitrogen Hydrate Cage Occupancy and Bulk Modulus Inferred from Density Functional Theory-Derived Cell Parameters

2021

International audience; Gas clathrate hydrate solid materials, ubiquitous in nature as found either on the ocean floor, permafrost on the Earth, or in extraterrestrial planets and comets, are also technologically relevant, for example, in energy storage or carbon dioxide sequestration. Nitrogen hydrate, in particular, is of great interest as a promoter of the kinetics of the methane replacement reaction by carbon dioxide in natural gas hydrates. This hydrate may also appear in the chemistry of planets wherever nitrogen constitutes the majority of the atmosphere. A fine understanding of the stability of this hydrate under various thermodynamic conditions is thus of utmost importance to asses…

A local chemical potential approach within the variable charge method formalism

2008

A new and computationally efficient implementation of the variable charge method of Streitz and Mintmire (1994 Phys. Rev. B 50 11996) is presented. In particular a local chemical potential approach that optimizes the charge on only those atoms expected to be ionic is developed. By doing so, the charge fluctuation problem experienced in regions far from any oxygen is solved, leading to a linear minimization problem of the electrostatic energy. In the dilute oxygen limit, such an approach can lead to at least an order of magnitude saving in computation.

Viscous fingering in magnetic fluids: numerical simulation of radial Hele–Shaw flow

1999

Abstract In this paper, the viscous fingering phenomena of the magnetic liquids in the case when the magnetic field is applied normally to the Hele–Shaw cell is investigated by the numerical simulation technique. It is shown that the magnetic field causes additional destabilization of the free interface arising at the air injection in the magnetic liquid. Here the peculiarities of the interface dynamics – inward motion of the tips of the fjords, the gyration radius dependence on the perimeter found by the numerical simulations are in good accordance with the experiments.

Flexible Magnetic Filaments and their Applications

2016

Discrete element simulations of crumpling of thin sheets

2009

Forced crumpling of stiff self-avoiding sheets is studied by discrete element simulations. Simulations display stress condensation and scaling of ridge energy in agreement with theoretical expectations for elastic and frictionless sheets, and extends such behavior to elasto-plastic sheets. Crumpling of ideally elastic and frictionless sheets is compared to that of elasto-plastic sheets and sheets with friction.

Acoustic vibrations of anisotropic nanoparticles

2009

Acoustic vibrations of nanoparticles made of materials with anisotropic elasticity and nanoparticles with non-spherical shapes are theoretically investigated using a homogeneous continuum model. Cubic, hexagonal and tetragonal symmetries of the elasticity are discussed, as are spheroidal, cuboctahedral and truncated cuboctahedral shapes. Tools are described to classify the different vibrations and for example help identify the modes having a significant low-frequency Raman scattering cross-section. Continuous evolutions of the modes starting from those of an isotropic sphere coupled with the determination of the irreducible representation of the branches permit some qualitative statements t…

Novel Carbon Nanotubes Rolled from 6,6,12-Graphyne: Double Dirac Points in 1D Material

2017

Two kinds of novel carbon nanotubes, namely, (N, 0) and (0, N) 6,6,12-graphyne nanotubes (6,6,12-GNTs), are constructed by rolling up the rectangular 6,6,12-graphyne sheets along two different sides into cylinders. The mechanical and electronic properties of 6,6,12-GNTs with varied N from 3 to 20 are investigated by using density functional theory. Unlike the single-wall carbon nanotubes, the Young’s moduli of 6,6,12-GNTs do not remain constant in the case of (N, 0), but the (0, N) tubes possess almost the same one around 0.32 TPa. The band structures and density of states are also exhibited in this work. When the tube sizes N are bigger than four, Dirac points appear at Fermi level in the …

Giant piezoelectricity in B/N doped 4,12,2-graphyne

2020

Abstract The effects of boron (B) and nitrogen (N) substitutions in 4,12,2-graphyne on its geometric structure and mechanical as well as electronic properties have been systematically investigated with the aid of density functional theory (DFT). The trend in the elastic properties of the substituted systems is determined by the doping positions and the type of the dopants. The Bader charge analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,2-graphyne, but instead tends to form a polar bond, or even possibly a charge-shift bond. In particular, an obvious in-plane piezoelectricity is induced by foreign atom substitutions owing to the deformation of the p…

Interfacial tension of the isotropic-nematic interface in suspensions of soft spherocylinders.

2005

The isotropic to nematic transition in a system of soft spherocylinders is studied by means of grand canonical Monte Carlo simulations. The probability distribution of the particle density is used to determine the coexistence density of the isotropic and the nematic phases. The distributions are also used to compute the interfacial tension of the isotropic--nematic interface, including an analysis of finite size effects. Our results confirm that the Onsager limit is not recovered until for very large elongation, exceeding at least L/D=40, with L the spherocylinder length and D the diameter. For smaller elongation, we find that the interfacial tension increases with increasing L/D, in agreem…