Why does charge transfer reduce the covalent component of a heteropolar bond?

[sunghyunKim]

In THE THEORY OF REALMATERIALS(Annu. Rev. Mater. Sci. 2000. 30:1–26),

Marvin L. Cohen states that

"Because charge transfer reduces the covalent component of a heteropolar bond, B0 is also reduced."

Can you explain that connection between charge transfer and covalent component of a heteropolar bond? or give me a some ref?

 

[DrDu]

Well, take for example H2. If you transfer an electron from one H to the other you end up with a valence bond structure H^+ H^-, i.e. an ionic structure. Hence charge transfer is much the same as saying that there are ionic contributions to the bond.