A H 2O molecule demonstrates high instantaneous asymmetry with coordination numbers varying from two 22 to four or even greater 23. For instances, the separation between adjacent oxygen atoms (d OO) was measured to vary from 2.70 to 3.00 Å 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 and the molecular size (the H-O bond length d H) changes from 0.970 to 1.001 Å 21. However, the structure order, the geometric symmetry, the size and the separation between molecules packing in water and ice (H 2O) and their correlation remain yet highly disputed, independent issues despite decades-long intensive investigation. Water and ice has attracted much attention because of its anomalies pertaining to issues from galaxy to geology, astrophysics, biology, climate and to our daily lives 1, 2, 3, 4, 5, 6, 7. We clarified that: i) liquid water prefers statistically the mono-phase of tetrahedrally-coordinated structure with fluctuation, ii) the low-density phase (supersolid phase as it is strongly polarized with even lower density) exists only in regions consisting molecules with fewer than four neighbors and, iii) repulsion between electron pairs on adjacent oxygen atoms dictates the cooperative relaxation of the segmented O:H-O bond, which is responsible for the performance of water and ice. cm −3), the d L and the d H, as a known input, one can resolve the rest quantities using this solution that is probing conditions or methods independent.With any one of the d OO, the density ρ(g

This solution reconciles: i) the d L and the d H symmetrization of the O:H-O bond in compressed ice, ii) the d OO relaxation of cooling water and ice and, iii) the d OO expansion of a dimer and between molecules at water surface.

We present herewith a solution to unifying the density, the structure order and symmetry, the size (H-O length d H) and the separation (d OO = d L + d H or the O:H length d L) of molecules packing in water and ice in terms of statistic mean. The structural symmetry and molecular separation in water and ice remain uncertain.

Density of ice vs water