A density-functional exchange identity is derived in a very simple manner through coordinate scaling for the external potential within the coupling-constant approach. It is observed that this identity may be expressed as a recursion relation which is especially useful for testing approximations to the exchange functional, and to its corresponding exchange potential, as part of a full density-functional calculation involving correlation as well as exchange. © 1996 The American Physical Society.

• Received 29 January 1996

DOI:https://doi.org/10.1103/PhysRevA.53.3140