Search Results
Gradient structure for optoelectronic models of semiconductors
2016, Mielke, Alexander, Peschka, Dirk, Rotundo, Nella, Thomas, Marita
We derive an optoelectronic model based on a gradient formulation for the relaxation of electron-, hole- and photon- densities to their equilibrium state. This leads to a coupled system of partial and ordinary differential equations, for which we discuss the isothermal and the non-isothermal scenario separately.
Thermomechanical modeling of energy-reaction-diffusion systems, including bulk-interface interactions : dedicated to Michel Frémond on the occasion of his seventieth birthday
2011, Mielke, Alexander, Frémond, Michel
We show that many couplings between parabolic systems for processes in solids can be formulated as a gradient system with respect to the total free energy or the total entropy. This includes Allen-Cahn, Cahn-Hilliard, and reaction-diffusion systems and the heat equation. For this, we write the coupled system as an Onsager system (X,F,K) defining the evolution $dot U$= - K(U) DF(U). Here F is the driving functional, while the Onsager operator K(U) is symmetric and positive semidefinite. If the inverse G=K-1 exists, the triple (X,F,G) defines a gradient system. Onsager systems are well suited to model bulk-interface interactions by using the dual dissipation potential ?*(U, ?)= ư .