Berlin 2018 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
BP: Fachverband Biologische Physik
BP 12: Computational Biophysics I
BP 12.1: Vortrag
Dienstag, 13. März 2018, 09:30–09:45, H 1058
Langevin modeling of targeted molecular dynamics: a novel approach to calculate equilibrium free energies from non-equilibrium simulations — •Steffen Wolf and Gerhard Stock — Bimolecular Dynamics, Institute of Physics, Albert-Ludwigs-University Freiburg, Germany
We present an approach to calculate free energy surfaces based on non-equilibrium biased molecular dynamics simulations. Based on a comparison of Jarzynskis equality and the Langevin equation we derive an expression for non-equilibrium friction factors ΓNEQ(x). Force fluctuations δ f(t) of a simulated trajectory ensemble were derived from targeted molecular dynamics simulations as constraint forces using a holonomic constraint Φ(t) = (x(t)−x0(t)−vct)2 = 0 with a constant constraint velocity vc. Using a NaCl/water test system, we show that a surprisingly high accuracy in the prediction of the equilibrium free energy profile can be achieved with a relatively small number of N= 30 simulations at comparatively high constraint velocities of >10 nm/ns. Non-equilibrium friction profiles however need at least N= 500 simulations to converge. Comparison with equilibrium simulations shows a general agreement between non-equilibrium and equilibrium-derived friction factors for vc → 0. The non-equilibrium factors however contain intrinsic constraint velocity dependence, and outperform equilibrium factor-based corrections. Our approach allows for the calculation of near-continuous ΓNEQ(x) profiles directly from non-equilibrium trajectories, and thus for the on-the-fly correction of non-equilibrium simulations to obtain equilibrium free energy profiles.