Abstract: The bridge force term in partition the H-Fforce is defined, which means the force acting on a nucleus Acoming from the overlap of electronic charge density, between atoms Band C. The bridge forces in molecules B₂H₆ and C₂H₄ etc. are computed by means of quantum chemical ab initio method. The results show that the effect of bridge force in normal molecules (e.g.C,H₄) can be neglected, but it may play a important role in multicentre bridge bond of electronic deficient molecules (e.g.B₂H₆). The equivalent point charge of the overlap force and its position in molecule B2H₆ are calculated. According to these data a electronic charge distribution diagram of molecule B₂H₆ is drawn, which may clearly represent the character of chemical bond in a molecule.

Key words: Multicentre bridge bond, H-F force, Boranes