Regensburg 2016 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 29: Poster - Active Matter, Microswimmers and -fluidics, Statistical Physics Biosystems

DY 29.10: Poster

Tuesday, March 8, 2016, 18:15–21:00, Poster C

Probing defects and correlations in the hydrogen-bond network of ab initio water — •Piero Gasparotto and Michele Ceriotti — Laboratory of Computational Science and Modeling, IMX, EPFL, 1015 Lausanne, Switzerland

Water is an unusual liquid and many of its unique properties are due to the presence of an highly-structured hydrogen-bond (HB) network that is populated by a wide variety of different coordination defects. Due to the structural constraints imposed by the HB network, coordination defects do not come alone, but clustered together. Here, we compute defect-resolved distribution functions from ab initio molecular dynamics to probe the radial and angular correlation between defects. In doing this, we shed light on how fluctuations from the ideal tetrahedral structure contribute to the total radial distribution function of liquid water. We also present a systematic comparison of the concentration of different defects and the structural correlations between them, with a variety of simulation protocols. For instance, we considered different temperature, system size, basis set, integrator timestep, cutoff for the plane waves, the modeling of van-der-Waals corrections, nuclear quantum effects or exact exchange. We also compare these results with those coming from empirical force field simulations. These comparisons show that regardless of the details of the choice of the water potential, the qualitative predictions of the defect distributions are very similar. The most significant effect can be attributed to dispersion interactions, that impact the most on the relative populations of the various defects.