In an interacting electron gas one may distinguish between the "proton-proton" dielectric constant, which is the ratio of the applied electric field to the resultant electric field, and the "proton-electron" dielectric constant, which is the ratio of the applied electric field to the resultant electric field plus effective exchange and correlation field as would be experienced by an electron. The relationship between these two quantities is derived and used to prove that two recently proposed expressions for the structure-dependent energy of a metal are identical.

• Received 30 January 1967

DOI:https://doi.org/10.1103/PhysRev.158.670