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In this article, we present a series of first principle density functional theory simulation results which have, reproduced the vibrational spectra for ice Ih and VIII obtained by neutron scattering. Detailed analysis of the pressure-dependent simulation results shows that there is an oxygen–oxygen (O–O) interaction between the nearest water molecules participating in the H-bonding and this interaction is 1.5 times stronger than the H-bond at an O–O distance R _oo of 2.7 Å observed in ice I. The O–O interaction strength increases rapidly to 2.3 times the H-bond at R _oo  = 2.5 Å. Analysis of the simulation results for ice VIII, shows that the strong O–O interaction only exists between H-bonded water molecules (i.e. O-H—O) and not for non-H-bonded water molecules, even when the O—O distances are similar. This discovery completely changed our view of H-bonding in water and ice, redefining the term of hydrogen-bonding between water–water molecules. Incorporation of this term may also help us to explain water anomalies. In addition short H-bonds ( R _oo  < 2.7 Å) exist in DNA and proteins, and are thought to play a role crucial in enzyme catalysis and function. Hence this result could have major implications in our understanding of enzyme-catalysis and biology.