Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 10: Glasses (joint session DY/DF/CPP)

DY 10.7: Talk

Tuesday, March 12, 2013, 11:15–11:30, H46

Excess free energy of supercooled liquids at disordered walls — •Ronald Benjamin and Jürgen Horbach — Institut für Theoretische Physik II - Soft Matter, Heinrich-Heine-Universität Düsseldorf

We perform NVT molecular dynamics simulations of a supercooled liquid confined between identical walls of two types. In the first case flat structureless walls, represented by an external field are considered. In the second case we consider disordered walls consisting of the same supercooled liquid frozen into an amorphous configuration. Using a thermodynamic integration scheme [R.Benjamin and J. Horbach, J. Chem. Phys. 137, 044707 (2012)] we are able to obtain the excess free energy of the supercooled liquid with respect to both kinds of walls. While a positive excess free energy (of the order of 10 k_B T / σ²) is obtained with respect to a flat structureless wall, the excess free energy between the supercooled liquid and the frozen disordered walls turns out to be negative (≈ −0.5 k_B T / σ²) even though the potential energy of the supercooled liquid in presence of the disordered walls is the same as that of the bulk. This shows the purely entropic contribution to the excess free energy of the supercooled liquid in presence of the disordered walls. The existence of a negative excess free energy also shows that the thermodynamic properties of such a confined supercooled liquid is not identical to that of the bulk.