hydrogen bond in theoretical organic chemistry

A particular type of multicenter (three center - four electron) X–H ...Y in which the central hydrogen atom covalently linked to an electronegative atom X (C, N, O, S..) forms an additional weaker bond with atom Y (N, O, S..) in the direction of its lone electron pair orbital. The energy of hydrogen bonds, which is usually in the range of $3$ – $15 kcal mol$ ( $12$ – $65 kJ mol$ ), results from the electrostatic interaction and also from the orbital interaction of the antibonding σ*(XH)MO of the molecule acting as the hydrogen donor and the non-bonding lone electron pair MOn_Y of the hydrogen acceptor molecule.

Source:

PAC, 1999, 71, 1919 (Glossary of terms used in theoretical organic chemistry) on page 1945