A B(r) function of electron system in solid is a real space expression equivalent to the distribution function of electron momentum density r(q) in momentum space and has a direct relation to Compton profile function J(qz). Through its characteristic contour behaviour, the function works as one of useful tools for understanding electronic bond structure.
In order to find a fundamental relation of the B(r) function to potential field for electrons, it has been utilized the fact that the function can be described in terms of autocorrelation between electron wave functions. On the basis of Schrödinger equation for the electron wave function, a differential equation for the B(r) function is derived in a simple functional form containing an autocorrelative term for the potential field. Some of general features of the equation has been discussed in relation to the potential term.