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Critical Behavior (critical + behavior)

Distribution by Scientific Domains
Chemistry50%

Selected Abstracts

Critical behavior in quenched random structures: Mean-field lattice-gas approach

AICHE JOURNAL, Issue 2 2001
S. De
A new mean-field equation-of-state model is proposed for predicting the critical behavior of fluids confined in porous, random structures. The approach is based on a lattice-gas formalism and incorporates effects of both fluid confinement and energetically heterogeneous interactions between fluid molecules and pore surfaces. The model was used to predict a variety of thermodynamic properties in these systems, including the dependence of the confined fluid's critical properties on the porosity and relative strength of fluid,fluid and fluid,pore interaction energies. The study of suface-energy heterogeneities show that they significantly affect the critical temperature of the confined fluid, at a given porosity, compared to the uniform energy case. Comparison of the model performance with both grand canonical Monte Carlo simulation results and a set of adsorption data in a silica gel suggest that the approach taken here provides a useful analytic method for calculating physical properties in complex systems of this kind. [source]

Critical behavior of KDCO3 from 2H and 39K single crystal NMR

MAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2008
Christophe Odin
Abstract Potassium hydrogenocarbonate KDCO3 presents an order/disorder phase transition at Tc, 353 K. The critical behavior of this phase transition was studied by single crystal 2H and 39K NMR. The evolution of the order parameter as a function of temperature is quantified, and the critical exponent was determined, indicating a transition close to a tricritical point. The 2H Zeeman relaxation rate is strongly increased near the transition temperature. By calculating the noncritical contribution to the Zeeman relaxation rate, we show that the observed relaxation rate clearly presents a pseudo-divergent behavior near Tc, with a logarithmic singularity. The nature of the phase transition is discussed in the light of these results. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Critical behavior in quenched random structures: Mean-field lattice-gas approach

AICHE JOURNAL, Issue 2 2001
S. De
A new mean-field equation-of-state model is proposed for predicting the critical behavior of fluids confined in porous, random structures. The approach is based on a lattice-gas formalism and incorporates effects of both fluid confinement and energetically heterogeneous interactions between fluid molecules and pore surfaces. The model was used to predict a variety of thermodynamic properties in these systems, including the dependence of the confined fluid's critical properties on the porosity and relative strength of fluid,fluid and fluid,pore interaction energies. The study of suface-energy heterogeneities show that they significantly affect the critical temperature of the confined fluid, at a given porosity, compared to the uniform energy case. Comparison of the model performance with both grand canonical Monte Carlo simulation results and a set of adsorption data in a silica gel suggest that the approach taken here provides a useful analytic method for calculating physical properties in complex systems of this kind. [source]

Magnetic properties of almost localized fermions revisited: spin dependent masses and quantum critical behavior

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2006
Jozef Spa
Abstract The magnetic properties of almost localized (heavy) quasiparticles have been a subject of renewed interest in recent years. This is caused by the discovery of spin dependent masses predicted by us some time ago, as well as quantum critical behavior at the metal,insulator boundary. We discuss those phenomena, as well as metamagnetic behavior. These phenomena are discussed by regarding Gutzwiller approach (in the slave-boson version) as the mean-field approach to the correlated electron systems. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Quantum criticality in ultracold atoms on optical lattices

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2005
Marcos Rigol
Abstract In recent years degenerate quantum gases confined in optical lattices developed as a new field of research bridging the areas of quantum optics, atomic physics, and condensed matter physics. It offers the possibility of manipulating quantum many-body systems with an unprecedented flexibility, so that they can be considered as analog simulators of condensed matter systems. Particularly interesting is the possibility of creating strongly correlated bosonic or fermionic systems. We review here recent numerical simulations, where quantum critical behavior is studied both in and out of equilibrium. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]