Artifacts in dynamical simulations of coarse-grained model lipid bilayers.

With special focus on dissipative particle dynamics simulations of anisotropic and complex soft matter, such as lipid bilayers in water, we have investigated the occurrence of artifacts in the results obtained from dynamical simulations of coarse-grained particle-based models. The particles are modeled by beads that interact via soft repulsive conservative forces (as defined in dissipative particle dynamics simulations), harmonic bond potentials, as well as bending potentials imparting stiffness to the lipid tails. Two different update schemes are investigated: dissipative particle dynamics with a velocity-Verlet-like integration scheme [G. Besold, I. Vattulainen, M. Karttunen, and J. M. Polson, Phys. Rev. E 63, R7611 (2000)] and Lowe-Andersen thermostatting [C. P. Lowe, Europhys. Lett. 47, 145 (1999)] with the standard velocity-Verlet integration algorithm. By varying the integration time step, we examine various physical quantities, in particular pressure profiles and kinetic bead temperatures, for their sensitivity to artifacts caused by the specific combination of integration technique and the thermostat. We then propose a simple fingerprint method that allows monitoring the presence of simulation artifacts.