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Sorin Bastea

Publications and source records attributed to Sorin Bastea.

8 recordsLinked to original sources
PubMed2006

Aggregation kinetics in a model colloidal suspension.

We present molecular dynamics simulations of aggregation kinetics in a colloidal suspension modeled as a highly asymmetric binary mixture. Starting from a configuration with largely uncorrelated colloidal particles the system relaxes by coagulation-fragmentation dynamics to a structured state of low-dimensionality clusters with an exponential size distribution. The results show that short-range repulsive interactions alone can give rise to so-called cluster phases. For the present model and probably other, more common colloids, the observed clusters appear to be equilibrium phase fluctuations induced by the entropic intercolloidal attractions.

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PubMed2005

Viscosity and mutual diffusion in strongly asymmetric binary ionic mixtures.

We present molecular dynamics simulation results for the viscosity and mutual diffusion constant of a strongly asymmetric binary ionic mixture. We compare the results with available theoretical models previously tested for much smaller asymmetries. For the case of viscosity we propose a predictive framework based on the linear mixing rule, while for mutual diffusion we discuss some consistency problems of widely used Boltzmann-equation-based models.

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PubMed2004

Generation of methane in the Earth's mantle: in situ high pressure-temperature measurements of carbonate reduction.

We present in situ observations of hydrocarbon formation via carbonate reduction at upper mantle pressures and temperatures. Methane was formed from FeO, CaCO(3)-calcite, and water at pressures between 5 and 11 GPa and temperatures ranging from 500 degrees C to 1,500 degrees C. The results are shown to be consistent with multiphase thermodynamic calculations based on the statistical mechanics of soft particle mixtures. The study demonstrates the existence of abiogenic pathways for the formation of hydrocarbons in the Earth's interior and suggests that the hydrocarbon budget of the bulk Earth may be larger than conventionally assumed.

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PubMed2003

Transport properties of dense fluid argon.

We calculate using molecular dynamics simulations the transport properties of realistically modeled fluid argon at pressures up to approximately 50 GPa and temperatures up to 3000 K. In this context, we provide a critique of some newer theoretical predictions for the diffusion coefficients of liquids and a discussion of the Enskog theory relevance under two different adaptations: modified Enskog theory and effective diameter Enskog theory. We also analyze a number of experimental data for the thermal conductivity of monoatomic and small diatomic dense fluids.

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PubMed2002

Hydrodynamics of binary fluid phase segregation.

Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field u when the system is segregated into two phases (at low temperatures) with a sharp interface between them. u satisfies the incompressible Navier-Stokes equations together with a jump boundary condition for the pressure across the interface which, in turn, moves with a velocity given by the normal component of u. Numerical simulations of the Vlasov-Boltzmann equations for shear flows parallel and perpendicular to the interface in a phase segregated mixture support this analysis. We expect similar behavior in real fluid mixtures.

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PubMed2002

Living polymers in a size-asymmetric electrolyte.

A living polymers transition is found in molecular dynamics simulations of a charge-symmetric size-asymmetric electrolyte with no anisotropic interactions. The fluid has strong polymeric character at low temperatures, where it consists of large, alternating-charge linear chains and rings in chemical equilibrium. A mean-field theory of chain association is consistent with the existence of such a transition. In the polymeric phase, the system is very weakly conducting or electrically insulating.

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