<< the unusual properties of liquid water, if compared with other liquids, has puzzled us for centuries because the basic structure of liquid water has remained unclear and has continued to be a matter of serious debate. >>
AA << show that there are two overlapped peaks hidden in the apparent “first diffraction peak” of the structure factor. One of them (ordinary peak) corresponds to the neighboring O–O [Oxygen-Oxygen bond] distance as in ordinary liquids, and the other (anomalous peak) corresponds to a longer distance. >>
the << anomalous peak arises from the most extended period of density wave associated with a tetrahedral water structure and is to be identified as the so-called first sharp diffraction peak >>
<< In contrast, the ordinary peak arises from the density wave characteristic of local structures lacking tetrahedral symmetry. This finding unambiguously proves the coexistence of two types of local structures in liquid water. >>
Rui Shi, Hajime Tanaka. Direct Evidence in the Scattering Function for the Coexistence of Two Types of Local Structures in Liquid Water. J. Am. Chem. Soc. doi: 10.1021/ jacs.9b11211. Jan 21, 2020.
https://pubs.acs.org/doi/10.1021/jacs.9b11211#
Water, water everywhere—and it's weirder than you think. University of Tokyo. Feb 4, 2020.
https://m.phys.org/news/2020-02-everywhereand-weirder.html
