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M. A.?Mu?ozEmail author F?de los Santos M M?Telo da Gama 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(1):73-79
A beautifully simple model introduced a couple of decades ago, Tooms
cellular automaton, revealed that non-equilibrium systems may exhibit
generic bistability, i.e. two-phase coexistence over a finite area of
the (two-dimensional) phase diagram, in violation of the equilibrium
Gibbs phase rule. In this paper we analyse two interfacial models,
describing more realistic situations, that share with Tooms model a
phase diagram with a broad region of phase coexistence.
An analysis of the interfacial models yields conditions for generic
bistability in terms of physically relevant parameters that may be
controlled experimentally. 相似文献
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We present results of calculations of the equilibrium surface tension and density profiles for the liquid-vapour interface of a binary mixture of Lennard-Jones 12-6 fluids. The calculations are based on a density-functional theory for the Helmholtz free energy of the inhomogeneous mixture. This is a ‘microscopic’ generalization of the van der Waals-Cahn-Hilliard theory for the interface of a binary mixture. Our calculations cover the full range of liquid-vapour coexistence and the whole range of concentration. We find a correlation between the excess surface tension of the mixture and the surface segregation (adsorption) of the species with the lower surface tension. The ways in which segregation and excess surface tension depend on the Lennard-Jones parameters of the pure components are briefly discussed. Our results for the excess surface tension of mixtures of Ar and N2 and Ar and CH4 are compared with experiment; the agreement is reasonable. 相似文献
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We investigate the nature of the ordered phase and the orientational correlations between adjacent layers of the confined three-dimensional self-assembled rigid rod model, on the cubic lattice. We find that the ordered phase at finite temperatures becomes uniaxial in the thermodynamic limit, by contrast to the ground state (partial) order where the orientation of the uncorrelated layers is perpendicular to one of the three lattice directions. The increase of the orientational correlation between layers as the number of layers increases suggests that the unconfined model may also exhibit uniaxial ordering at finite temperatures. 相似文献
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Nelsen SF Weaver MN Zink JI Telo JP 《Journal of the American Chemical Society》2005,127(30):10611-10622
The optical spectra of nine dinitroaromatic radical anions (1,2- and 1,4-dinitrobenzene, 1,5- and 2,6-dinitro naphthalene, 4,4'-dinitrobiphenyl, 2,7-dinitro-9,9-dimethylfluorene, 2,6-dinitroanthracene, and 2,7- and 1,8-dinitrobiphenylene) in dimethylformamide are reported and analyzed. All have delocalized charge distribution, as demonstrated by the vibrational fine structure that is observed in their optical spectra: All show lowest energy absorption bands that correspond to an alpha-homo (highest occupied molecular orbital) to alpha-lumo (lowest unoccupied) transition, as shown by Koopmans-based UB3LYP calculation of the orbital separation of the neutral at the geometry of the radical anion. These single-point calculations are shown to be significantly more accurate for five of these compounds than the much more complex and expensive TD-DFT method. The two-state model should not be used to estimate the electronic coupling in delocalized intervalence compounds such as these. Neighboring orbital estimation of the electronic couplings show that using the two-state model greatly underestimates electronic coupling here. 相似文献
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Tasinkevych M Silvestre NM Patrício P Telo da Gama MM 《The European physical journal. E, Soft matter》2002,9(4):341-347
The interaction between two disks immersed in a 2D nematic is investigated i) analytically using the tensor order parameter
formalism for the nematic configuration around isolated disks and ii) numerically using finite-element methods with adaptive
meshing to minimize the corresponding Landau-de Gennes free energy. For strong homeotropic anchoring, each disk generates
a pair of defects with one-half topological charge responsible for the 2D quadrupolar interaction between the disks at large
distances. At short distance, the position of the defects may change, leading to unexpected complex interactions with the
quadrupolar repulsive interactions becoming attractive. This short-range attraction in all directions is still anisotropic.
As the distance between the disks decreases, their preferred relative orientation with respect to the far-field nematic director
changes from oblique to perpendicular.
Received 1 October 2002 and Received in final form 12 November 2002
RID="a"
ID="a"e-mail: miko@cii.fc.ul.pt 相似文献
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Fenistein D Bonn D Rafaï S Wegdam GH Meunier J Parry AO da Gama MM 《Physical review letters》2002,89(9):096101
We study the thickness of wetting layers in the binary-liquid mixture cyclohexane methanol. Far from the bulk critical point, the wetting layer thickness is independent of temperature, resulting from the competition between van der Waals and gravitational forces. Upon approaching the bulk critical temperature [t=(T(c)-T)/T(c)-->0], we observe that the wetting layer thickness diverges as t(-beta) with effective critical exponent beta=0.23+/-0.06. This is characteristic of a broad, intermediate scaling regime for the crossover from van der Waals wetting to critical scaling. We predict beta=beta/3 approximately 0.11, with beta the usual bulk-order parameter critical exponent, showing a small but significant difference with experiment. 相似文献