See the specific fragments of two molecules (They are the optimized structures). I started a with very innocent question, may I see the effect of hydrogen bondings on IR spectra (at a theoretical level)? Indeed I saw. But the vibrations appeared as confusing. They behave as symmetric and anti-symmetric vibrations around oxygen X rather than individual OH strechings. What is happening? Do the hydrogens feel that they both belong the oxygen X due to strong interaction? Is it possible ?