The temperature dependence of intermediate range oxygen-oxygen correlations in liquid water

We analyze the recent temperature dependent oxygen-oxygen pair-distribution functions from experimental high-precision x-ray diffraction data of bulk water by Skinner et al. [J. Chem. Phys. 141, 214507 (2014)] with particular focus on the intermediate range where small, but significant, correlations are found out to 17 angstrom. The second peak in the pair-distribution function at 4.5 angstrom is connected to tetrahedral coordination and was shown by Skinner et al. to change behavior with temperature below the temperature of minimum isothermal compressibility. Here we show that this is associated also with a peak growing at 11 angstrom which strongly indicates a collective character of fluctuations leading to the enhanced compressibility at lower temperatures. We note that the peak at similar to 13.2 angstrom exhibits a temperature dependence similar to that of the density with a maximum close to 277 K or 4 degrees C. We analyze simulations of the TIP4P/2005 water model in the same manner and find excellent agreement between simulations and experiment albeit with a temperature shift of similar to 20 K. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).