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Density functional theory and molecular dynamics simulation of poly(dimethylsiloxane) melts near silica surfaces

Proposed for publication in Macromolecules.

Curro, John G.; Frischknecht, Amalie L.

Classical density functional theory (DFT) is applied to study properties of fully detailed, realistic models of poly(dimethylsiloxane) liquids near silica surfaces and compared to results from molecular dynamics simulations. In solving the DFT equations, the direct correlation functions are obtained from the polymer reference interaction site model (PRISM) theory for the repulsive parts of the interatomic interactions, and the attractions are treated via the random-phase approximation (RPA). Good agreement between density profiles calculated from DFT and from the simulations is obtained with empirical scaling of the direct correlation functions. Separate scaling factors are required for the PRISM and RPA parts of the direct correlation functions. Theoretical predictions of stress profiles, normal pressure, and surface tensions are also in reasonable agreement with simulation results.

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TYPE Journal Article YEAR 2005
OSTI

Large-scale stabilized FE computational analysis of nonlinear steady state transport/reaction systems

Proposed for publication in Computer Methods in Applied Mechanics and Engineering.

Shadid, John N.; Salinger, Andrew G.; Pawlowski, Roger; Lin, Paul T.; Hennigan, Gary L.; Tuminaro, Raymond S.; Lehoucq, Rich

The solution of the governing steady transport equations for momentum, heat and mass transfer in fluids undergoing non-equilibrium chemical reactions can be extremely challenging. The difficulties arise from both the complexity of the nonlinear solution behavior as well as the nonlinear, coupled, non-symmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this paper, we briefly review progress on developing a stabilized finite element (FE) capability for numerical solution of these challenging problems. The discussion considers the stabilized FE formulation for the low Mach number Navier-Stokes equations with heat and mass transport with non-equilibrium chemical reactions, and the solution methods necessary for detailed analysis of these complex systems. The solution algorithms include robust nonlinear and linear solution schemes, parameter continuation methods, and linear stability analysis techniques. Our discussion considers computational efficiency, scalability, and some implementation issues of the solution methods. Computational results are presented for a CFD benchmark problem as well as for a number of large-scale, 2D and 3D, engineering transport/reaction applications.

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TYPE Journal Article YEAR 2005
OSTI
Results 86476–86500 of 99,299
Results 86476–86500 of 99,299