“…In addition, several literature values of the first peak in the radial O-O pair correlation function deduced either from x-ray scattering 9,15 or from a combined analysis 14 of several older x-ray 10,60,61 and neutron scattering 62,63 As is well-known, the unusual thermal evolution of the mass density of water is governed not simply by inter-molecular bond expansion but also by a complex structural reorganization. 67 To take this into account, we set up a slightly more complex yet still simplistic geometric model that approximates the water molecules as spheres, an approach that is supported by x-ray scattering results. 10 Thereby, the oxygen atom is in the center of the sphere with a radius equal to half the length of an inter-molecular H-bond (i.e., rs = 0.5 × D OH⋅ ⋅ ⋅O ), and the hydrogen atoms are located roughly at the surface of this sphere corresponding to two of the edges of an inscribed tetrahedron (actually, the surface of the sphere, would cut the inter-molecular H-bond in half, which means that the covalently bound hydrogen atoms are considerably closer to the center).…”