Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 22: Statistical Physics (general)

DY 22.4: Talk

Wednesday, March 13, 2013, 15:45–16:00, H48

Grand-Canonical-like molecular dynamics — •Han Wang, Carsten Hartmann, Christof Schuette, and Luigi Delle Site — Institute for Mathematics, Freie Univ. Berlin

In this presentation, we describe a general theoretical analysis, and show numerical tests of the reliability of the adaptive resolution simulation (AdResS) technique in sampling the Grand Canonical ensemble. We demonstrate that the correct density and radial distribution functions in the hybrid region, where molecules change resolution, are two necessary conditions for considering the atomistic and coarse-grained regions in AdResS equivalent to subsystems of a full atomistic system with an accuracy up to the second order with respect to the probability distribution of the system. Moreover, we show that the work done by a thermodynamic force in the transition region, that is a force originally derived on the basis of empirical thermodynamic considerations, is formally equivalent to balance the chemical potential difference between the different resolutions. From these results follows the main conclusion that the atomistic region exchanges molecules with the coarse-grained region in a Grand Canonical fashion with an accuracy up to (at least) second order. Numerical tests, for the relevant case of liquid water at ambient conditions, are carried out to strengthen the conclusions of the theoretical analysis. This fruitful combination of theoretical principles and numerical evidence candidates the adaptive resolution technique as a natural, general and efficient protocol for Grand Canonical Molecular Dynamics for the case of large systems.