Berlin 2018 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

CPP: Fachverband Chemische Physik und Polymerphysik

CPP 79: Wetting, Microfluidics and Confined Liquids II

CPP 79.7: Vortrag

Freitag, 16. März 2018, 11:00–11:15, PC 203

Metadynamics calculation of chemical potential in dense and confined fluids — •Claudio Perego¹ and Michele Parrinello² — ¹Max Planck Institute for Polymer Research, Mainz (De) — ²Swiss Federal Institute of Technology, Zurich (Ch)

Chemical potential is a crucial thermodynamic quantity, regulating phase and chemical equilibria in a wide range of systems. The calculation of chemical potential in dense fluids represents a long-standing challenge in molecular simulations. An established approach builds on Widom's method, in which chemical potential is computed by sampling the insertion energy of a test particle. The resulting value is mostly determined by low energy insertions, in which the test particle is placed in a proper cavity within the system particles. In dense liquids such cavities are rarely available, and the sampling is restricted to large insertion energies, preventing the convergence of the estimate. Here we present a new method for computing the chemical potential in dense liquids. The technique builds on metadynamics to extend the insertion energies to the relevant low energy region, inaccessible in unbiased simulations. We show that the method can be also generalized for the computation of chemical potential in non-homogeneous fluids, which represents a crucial step for the study of nano-fluidics and confined liquids. The technique is then tested with both homogeneous and non-homogeneous Lennard-Jones fluids. As a result accurate chemical potential estimates are obtained even at large densities, where the classical approach fails.